Antibody therapeutics that bind CD123

ABSTRACT

There is disclosed compositions and methods relating to or derived from anti-CD123 antibodies. More specifically, there is disclosed fully human antibodies that bind CD123, CD123-antibody binding fragments and derivatives of such antibodies, and CD123-binding polypeptides comprising such fragments. Further still, there is disclosed nucleic acids encoding such antibodies, antibody fragments and derivatives and polypeptides, cells comprising such polynucleotides, methods of making such antibodies, antibody fragments and derivatives and polypeptides, and methods of using such antibodies, antibody fragments and derivatives and polypeptides, including methods of treating a disease.

RELATED APPLICATION

This application claims priority to U.S. Provisional Application 62/144,899, filed on Apr. 8, 2015, the entire contents of which are incorporated by reference in their entirety herein.

TECHNICAL FIELD

The present disclosure provides compositions and methods relating to or derived from anti-CD123 antibodies. More specifically, the present disclosure provides fully human antibodies that bind CD123, CD123-antibody binding fragments and derivatives of such antibodies, and CD123-binding polypeptides comprising such fragments. Further still, the present disclosure provides nucleic acids encoding such antibodies, antibody fragments and derivatives and polypeptides, cells comprising such polynucleotides, methods of making such antibodies, antibody fragments and derivatives and polypeptides, and methods of using such antibodies, antibody fragments and derivatives and polypeptides, including methods of treating a disease.

BACKGROUND

Hematological cancer conditions are the types of cancer such as leukemia and malignant lymphoproliferative conditions that affect blood, hone marrow and the lymphatic system. Leukemia can be classified as acute leukemia and chronic leukemia. Acute leukemia can be further classified as acute myelogenous leukemia (AML) and acute lymphoid leukemia (ALL). Chronic leukemia includes chronic myelogenous leukemia (CML) and chronic lymphoid leukemia (CLL). Other related conditions include myelodysplastic syndromes (MDS, formerly known as “preleukemia”) which are a diverse collection of hematological conditions united by ineffective production (or dysplasia) of myeloid blood cells and risk of transformation to AML. Leukemic stem cells (LSCs) are cancer cells that possess characteristics associated with normal stem cells, that is, the property of self-renewal and the capability to develop multiple lineages. Such cells are proposed to persist in hematological cancers such as AML as distinct populations.

Acute myelogenous leukemia (AML) is a clonal disorder clinically presenting as increased proliferation of heterogeneous and undifferentiated myeloid blasts. The leukemic hierarchy is maintained by a small population of LSCs, which have the distinct ability for self-renewal, and are able to differentiate into leukemic progenitors. These progenitors generate the large numbers of leukemic blasts readily detectable in patients at diagnosis and relapse, leading ultimately to mortality. AML-LSC have been commonly reported as quiescent cells, in contrast to rapidly dividing clonogenic progenitors. This property of LSCs renders conventional chemotherapeutics that target proliferating cells less effective, potentially explaining the current experience in which a high proportion of AML patients enter complete remission, often relapse, with <30% of adults surviving for more than 4 years. In addition, minimal residual disease occurrence and poor survival has been attributed to high LSC frequency at diagnosis in AML, patients.

AML-LSCs and normal hematopoietic stem cells (HSCs) share the common properties of slow division, self-renewal ability, and surface markers such as the CD34⁺CD38⁺ phenotype. Nevertheless, LSCs have been reported to possess enhanced self-renewal activity, in addition to altered expression of other cell surface markers, both of which present targets for therapeutic exploitation, Interleukin-3 (IL-3) mediates its action through interaction with cell surface receptors that consist of 2 subunits, an α subunit (CD123) and a β common (β_(c)) chain (CD 131). The interaction of an α chain with a β chain forms a high affinity receptor for IL-3, and the β_(c) chain mediates the subsequent signal transduction. Over-expression of CD123 on AML, blasts, CD34⁺ leukemic progenitors and LSCs relative to normal hematopoietic cells has been widely reported, and has been proposed as a marker of LSCs in some studies. CD131 was also reported to be expressed on AML cells but there are conflicting reports on its expression on AML-LSCs.

Over-expression of CD123 on AML cells confers a range of growth advantages over normal hematopoietic cells, with a large proportion of AML blasts reported to proliferate in culture in response to IL-3. Moreover, high-level CD123 expression on AML cells has been correlated with: the level of IL-3-stimulated STAT-5 activation; the proportion of cycling cells; more primitive cell surface phenotypes and resistance to apoptosis. Clinically, high CD123 expression in AML is associated with lower survival duration, a lower complete remission rate and higher blast counts at diagnosis.

U.S. Pat. No. 6,177,078 discloses the anti-IL-3 Receptor alpha chain (IL-3Rα) monoclonal antibody 7G3, and the ability of 703 to bind to the N-terminal domain, specifically amino acid residues 19-49, of IL-3Rα. U.S. Pat. No. 6,733,743 discloses a method of impairing a hematologic cancer progenitor cell that expresses CD123 but does not significantly express CD131, by contacting the cell with a composition of an antibody and a cytotoxic agent (selected from a chemotherapeutic agent, a toxin or an alpha-emitting radioisotope) whereby the composition binds selectively to CD 123 in an amount effective to cause cell death. The hematologic cancer may leukemia or a malignant lymphoproliferative disorder such as lymphoma.

SUMMARY

This invention pertains to proteins capable of binding to CD123 (e.g., human CD123_(—) including anti-CD123 antibodies, and antigen-binding fragments thereof. The present disclosure provides an isolated fully human antibody of an IgG class that binds to a CD123 epitope, wherein said antibody comprises a heavy chain variable domain sequence that is at least 95% identical, at least 96% identical, at least 97% identical, at least 98% identical, or at least 99% identical, to an amino acid sequence selected from the group consisting of

SEQ ID NO. 1, SEQ ID NO. 3, SEQ ID NO. 5, SEQ ID NO. 6, SEQ ID NO. 7, SEQ ID NO. 9, SEQ ID NO. 11, SEQ ID NO. 13, SEQ ID NO. 15, SEQ ID NO. 17, SEQ ID NO. 19, SEQ ID NO. 21, SEQ ID NO. 23, SEQ ID NO. 25, SEQ ID NO. 27, and combinations thereof, and that has a light chain variable domain sequence that is at least 95% identical, at least 96% identical, at least 97% identical, at least 98% identical, or at least 99% identical, to the amino acid sequence consisting of SEQ ID NO. 2, SEQ ID NO. 4, SEQ ID NO. 6, SEQ ID NO. 8, SEQ ID NO. 10, SEQ ID NO. 12, SEQ ID NO. 14, SEQ ID NO. 16, SEQ ID NO. 18, SEQ ID NO. 20, SEQ ID NO. 22, SEQ ID NO. 24, SEQ ID NO. 26, SEQ ID NO. 28, and combinations thereof.

The present disclosure further provides a fully human antibody of an IgG class that binds to a CD123 epitope with a binding affinity of at least 10⁻⁶M, which has a heavy chain variable domain sequence that is at least 95% identical, at least 96% identical, at least 97% identical, at least 98% identical, or at least 99% identical, to an amino acid sequence selected SEQ ID NO. 1, SEQ ID NO. 3, SEQ ID NO. 5, SEQ ID NO. 6, SEQ ID NO. 7, SEQ ID NO. 9, SEQ ID NO. 11, SEQ ID NO. 13, SEQ ID NO. 15, SEQ ID NO. 17, SEQ ID NO. 19, SEQ ID NO. 21, SEQ ID NO. 23, SEQ ID NO. 25, SEQ ID NO. 27, and combinations thereof, and that has a light chain variable domain sequence that is at least 95% identical, at least 96% identical, at least 97% identical, at least 98% identical, or at least 99% identical, to the amino acid sequence consisting of SEQ ID NO. 2, SEQ ID NO. 4, SEQ ID NO. 6, SEQ ID NO. 8, SEQ ID NO. 10, SEQ ID NO. 12, SEQ ID NO. 14, SEQ ID NO. 16, SEQ ID NO. 18, SEQ ID NO. 20, SEQ ID NO. 22, SEQ ID NO. 24, SEQ ID NO. 26, SEQ ID NO. 28, and combinations thereof.

In one aspect, the present disclosure provides an isolated fully human anti-CD123 antibody comprising a heavy chain domain sequence as set forth in an amino acid sequence selected from the group consisting of SEQ ID NO. 1, SEQ ID NO. 3, SEQ ID NO. 5, SEQ ID NO. 6, SEQ ID NO. 7, SEQ ID NO. 9, SEQ ID NO. 11, SEQ ID NO. 13, SEQ ID NO. 15, SEQ ID NO. 17, SEQ ID NO. 19, SEQ ID NO. 21, SEQ ID NO. 23, SEQ ID NO. 25, and SEQ ID NO. 27; and comprising a light chain variable domain sequence as set forth in an amino acid sequence selected from the group consisting of SEQ ID NO. 2, SEQ ID NO. 4, SEQ ID NO. 6, SEQ ID NO. 8, SEQ ID NO. 10, SEQ ID NO. 12, SEQ ID NO. 14, SEQ ID NO. 16, SEQ ID NO. 18, SEQ ID NO. 20, SEQ ID NO. 22, SEQ ID NO. 24, SEQ ID NO. 26, and SEQ ID NO. 28.

In one embodiment, the fully human antibody has both a heavy chain and a light chain wherein the antibody has a heavy chain/light chain variable domain sequence selected from the group consisting SEQ ID NO. 1/SEQ ID NO. 2 (called LAA3 herein), SEQ ID NO. 3/SEQ ID NO. 4 (called LAA4 herein), SEQ ID NO. 5/SEQ ID NO. 6 (called LAA6 herein), SEQ ID NO. 7/SEQ ID NO. 8 (called LAA8 herein), SEQ ID NO. 9/SEQ ID NO. 10 (called LAB11 herein), SEQ ID NO. 11/SEQ ID NO. 12 (called LAB2 herein), SEQ ID NO. 13/SEQ ID NO. 14 (called LAC11 herein), SEQ ID NO. 15/SEQ ID NO. 16 (called LAC12 herein), SEQ ID NO. 17/SEQ ID NO. 18 (called LAE4 herein), SEQ ID NO. 19/SEQ ID NO. 20 (called LAF5 herein), SEQ ID NO. 21/SEQ ID NO. 22 (called LAF7 herein), SEQ ID NO. 23/SEQ ID NO. 24 (called LAG12 herein), SEQ ID NO. 25/SEQ ID NO. 26 (called LAH3), SEQ ID NO. 27/SEQ ID NO. 28 (called LAH5 herein), and combinations thereof.

In one embodiment, the present disclosure provides an anti-CD123 fully human antibody Fab fragment, having a variable domain region from a heavy chain and a variable domain region from a light chain, wherein the heavy chain variable domain sequence that is at least 95% identical, at least 96% identical, at least 97% identical, at least 98% identical, or at least 99% identical, to an amino acid sequence selected from the group consisting of SEQ ID NO. 1, SEQ ID NO. 3, SEQ ID NO. 5, SEQ ID NO. 6, SEQ ID NO. 7, SEQ ID NO. 9, SEQ ID NO. 11, SEQ ID NO. 13, SEQ ID NO. 15, SEQ ID NO. 17, SEQ ID NO. 19, SEQ ID NO. 21, SEQ ID NO. 23, SEQ ID NO. 25, SEQ ID NO. 27, and combinations thereof, and comprises a light chain variable domain comprising an amino acid sequence that is at least 95% identical, at least 96% identical, at least 97% identical, at least 98% identical, or at least 99% identical, to an amino acid sequence selected from the group consisting of SEQ ID NO. 2, SEQ ID NO. 4, SEQ ID NO. 6, SEQ ID NO. 8, SEQ ID NO. 10, SEQ ID NO. 12, SEQ ID NO. 14, SEQ ID NO. 16, SEQ ID NO. 18, SEQ ID NO. 20, SEQ ID NO. 22, SEQ ID NO. 24, SEQ ID NO. 26, SEQ ID NO. 28, and combinations thereof. In one embodiment, the fully human antibody Fab fragment has both a heavy chain variable domain region and a light chain variable domain region wherein the antibody has a heavy chain/light chain variable domain sequence selected from the group consisting SEQ ID NO. 1/SEQ ID NO. 2, SEQ ID NO. 3/SEQ ID NO. 4, SEQ ID NO. 5/SEQ ID NO. 6, SEQ ID NO. 7/SEQ ID NO. 8, SEQ ID NO. 9/SEQ ID NO. 10, SEQ ID NO. 11/SEQ ID NO. 12, SEQ ID NO. 13/SEQ ID NO. 14, SEQ ID NO. 15/SEQ ID NO. 16, SEQ ID NO. 17/SEQ ID NO. 18, SEQ ID NO. 19/SEQ ID NO. 20, SEQ ID NO. 21/SEQ ID NO. 22, SEQ ID NO. 23/SEQ ID NO. 24, SEQ ID NO. 25/SEQ ID NO. 26, SEQ ID NO. 27/SEQ ID NO. 28, and combinations thereof.

In one embodiment, the invention features a fully human antibody Fab fragment, comprising a heavy chain variable domain and a light chain variable domain, wherein the heavy chain domain comprises an amino acid sequence selected from the group consisting of SEQ ID NO. 1, SEQ ID NO. 3, SEQ ID NO. 5, SEQ ID NO. 6, SEQ ID NO. 7, SEQ ID NO. 9, SEQ ID NO. 11, SEQ ID NO. 13, SEQ ID NO. 15, SEQ ID NO. 17, SEQ ID NO. 19, SEQ ID NO. 21, SEQ ID NO. 23, SEQ ID NO. 25, and SEQ ID NO. 27; and comprising a light chain variable domain sequence as set forth in an amino acid sequence selected from the group consisting of SEQ ID NO. 2, SEQ ID NO. 4, SEQ ID NO. 6, SEQ ID NO. 8, SEQ ID NO. 10, SEQ ID NO. 12, SEQ ID NO. 14, SEQ ID NO. 16, SEQ ID NO. 18, SEQ ID NO. 20, SEQ ID NO. 22, SEQ ID NO. 24, SEQ ID NO. 26, and SEQ ID NO. 28.

In another aspect, the present disclosure provides an anti-CD123 single chain human antibody, having a variable domain region from a heavy chain and a variable domain region from a light chain and a peptide linker connecting the heavy chain and light chain variable domain regions, wherein the heavy chain variable domain comprises an amino acid sequence that is at least 95% identical, at least 96% identical, at least 97% identical, at least 98% identical, or at least 99% identical, to an amino acid sequence selected from the group consisting of SEQ ID NO. 1, SEQ ID NO. 3, SEQ ID NO. 5, SEQ ID NO. 6, SEQ ID NO. 7, SEQ ID NO. 9, SEQ ID NO. 11, SEQ ID NO. 13, SEQ ID NO. 15, SEQ ID NO. 17, SEQ ID NO. 19, SEQ ID NO. 21, SEQ ID NO. 23, SEQ ID NO. 25, SEQ ID NO. 27, and wherein the light chain variable domain comprises an amino acid sequence that is at least 95% identical, at least 96% identical, at least 97% identical, at least 98% identical, or at least 99% identical, to an amino acid sequence selected from the group consisting of SEQ ID NO. 2, SEQ ID NO. 4, SEQ ID NO. 6, SEQ ID NO. 8, SEQ ID NO. 10, SEQ ID NO. 12, SEQ ID NO. 14, SEQ ID NO. 16, SEQ ID NO. 18, SEQ ID NO. 20, SEQ ID NO. 22, SEQ ID NO. 24, SEQ ID NO. 26, SEQ ID NO. 28, and combinations thereof.

In one embodiment, the invention includes a fully human single chain antibody comprising both a heavy chain variable domain region and a light chain variable domain region, wherein the single chain fully human antibody has a heavy chain/light chain variable domain sequence selected from the group consisting of SEQ ID NO. 1/SEQ ID NO. 2, SEQ ID NO. 3/SEQ ID NO. 4, SEQ ID NO. 5/SEQ ID NO. 6, SEQ ID NO. 7/SEQ ID NO. 8, SEQ ID NO. 9/SEQ ID NO. 10, SEQ ID NO. 11/SEQ ID NO. 12, SEQ ID NO. 13/SEQ ID NO. 14, SEQ ID NO. 15/SEQ ID NO. 16, SEQ ID NO. 17/SEQ ID NO. 18, SEQ ID NO. 19/SEQ ID NO. 20, SEQ ID NO. 21/SEQ ID NO. 22, SEQ ID NO. 23/SEQ ID NO. 24, SEQ ID NO. 25/SEQ ID NO. 26, SEQ ID NO. 27/SEQ ID NO. 28, and combinations thereof.

In another aspect, the present disclosure provides an anti-CD123 single chain human antibody, comprising a variable domain region from a heavy chain and a variable domain region from a light chain and a peptide linker connecting the heavy chain and light chain variable domain regions, wherein the heavy chain variable domain comprises an amino acid sequence selected from the group consisting of SEQ ID NO. 1, SEQ ID NO. 3, SEQ ID NO. 5, SEQ ID NO. 6, SEQ ID NO. 7, SEQ ID NO. 9, SEQ ID NO. 11, SEQ ID NO. 13, SEQ ID NO. 15, SEQ ID NO. 17, SEQ ID NO. 19, SEQ ID NO. 21, SEQ ID NO. 23, SEQ ID NO. 25, and SEQ ID NO. 27, and wherein the light chain variable domain comprises an amino acid sequence selected from the group consisting of SEQ ID NO. 2, SEQ ID NO. 4, SEQ ID NO. 6, SEQ ID NO. 8, SEQ ID NO. 10, SEQ ID NO. 12, SEQ ID NO. 14, SEQ ID NO. 16, SEQ ID NO. 18, SEQ ID NO. 20, SEQ ID NO. 22, SEQ ID NO. 24, SEQ ID NO. 26, and SEQ ID NO. 28.

Also included, is an isolated anti-CD123 antibody, or antigen-binding fragment thereof, comprising a heavy chain variable domain comprising complementarity determining regions (CDRs) as set forth in a heavy chain variable region amino acid sequence selected from the consisting of SEQ ID NO. 1, SEQ ID NO. 3, SEQ ID NO. 5, SEQ ID NO. 6, SEQ ID NO. 7, SEQ ID NO. 9, SEQ ID NO. 11, SEQ ID NO. 13, SEQ ID NO. 15, SEQ ID NO. 17, SEQ ID NO. 19, SEQ ID NO. 21, SEQ ID NO. 23, SEQ ID NO. 25, and SEQ ID NO. 27, and comprising a light chain variable region comprising CDRs as set forth in a light chain variable region amino acid sequence selected from the group consisting of SEQ ID NO. 2, SEQ ID NO. 4, SEQ ID NO. 6, SEQ ID NO. 8, SEQ ID NO. 10, SEQ ID NO. 12, SEQ ID NO. 14, SEQ ID NO. 16, SEQ ID NO. 18, SEQ ID NO. 20, SEQ ID NO. 22, SEQ ID NO. 24, SEQ ID NO. 26, and SEQ ID NO. 28.

In one embodiment, the anti-CD123 fully human antibody or antibody fragment has a heavy chain variable domain that is at least 95% identical, at least 96% identical, at least 97% identical, at least 98% identical, or at least 99% identical, to an amino acid sequence selected from the group consisting of SEQ ID NO. 1, SEQ ID NO. 3, SEQ ID NO. 5, SEQ ID NO. 6, SEQ ID NO. 7, SEQ ID NO. 9, SEQ ID NO. 11, SEQ ID NO. 13, SEQ ID NO. 15, SEQ ID NO. 17, SEQ ID NO. 19, SEQ ID NO. 21, SEQ ID NO. 23, SEQ ID NO. 25, SEQ ID NO. 27, and combinations thereof, and has a light chain variable domain comprising an amino acid sequence that is at least 95% identical, at least 96% identical, at least 97% identical, at least 98% identical, or at to the amino acid consisting of SEQ ID NO. 2, SEQ ID NO. 4, SEQ ID NO. 6, SEQ ID NO. 8, SEQ ID NO. 10, SEQ ID NO. 12, SEQ ID NO. 14, SEQ ID NO. 16, SEQ ID NO. 18, SEQ ID NO. 20, SEQ ID NO. 22, SEQ ID NO. 24, SEQ ID NO. 26, SEQ ID NO. 28, and combinations thereof. In one embodiment, the fully human antibody, or antibody fragment, comprises a heavy chain variable domain comprising an amino acid

sequence selected from the group consisting of SEQ ID NO. 1, SEQ ID NO. 3, SEQ ID NO. 5, SEQ ID NO. 7, SEQ ID NO. 9, SEQ ID NO. 11, SEQ ID NO. 13, SEQ ID NO. 15, SEQ ID NO. 17, SEQ ID NO. 19, SEQ ID NO. 21, SEQ ID NO. 23, SEQ ID NO. 25, SEQ ID NO. 27, and combinations thereof, and comprises a light chain variable domain comprising an amino acid sequence selected from the group consisting of SEQ ID NO. 2, SEQ ID NO. 4, SEQ ID NO. 6, SEQ ID NO. 8, SEQ ID NO. 10, SEQ ID NO. 12, SEQ ID NO. 14, SEQ ID NO. 16, SEQ ID NO. 18, SEQ ID NO. 20, SEQ ID NO. 22, SEQ ID NO. 24, SEQ ID NO. 26, SEQ ID NO. 28, and combinations thereof.

In certain embodiments, the anti-CD123 fully human antibody has both a heavy chain and a light chain wherein the antibody has a heavy chain/light chain variable domain sequence selected from the group consisting of SEQ ID NO. 1/SEQ ID NO. 2 (called LAA3 herein), SEQ ID NO. 3/SEQ ID NO. 4 (called LAA4 herein), SEQ ID NO. 5/SEQ ID NO. 6 (called LAA6 herein), SEQ ID NO. 7/SEQ ID NO. 8 (called LAA8 herein), SEQ ID NO. 9/SEQ ID NO. 10 (called LAB11 herein), SEQ ID NO. 11/SEQ ID NO. 12 (called LAB2 herein), SEQ ID NO. 13/SEQ ID NO. 14 (called LAC11 herein), SEQ ID NO. 15/SEQ ID NO. 16 (called LAC12 herein), SEQ ID NO. 17/SEQ ID NO. 18 (called LAE4 herein), SEQ ID NO. 19/SEQ ID NO. 20 (called LAF5 herein), SEQ ID NO. 21/SEQ ID NO. 22 (called LAF7 herein), SEQ ID NO. 23/SEQ ID NO. 24 (called LAG12 herein), SEQ ID NO. 25/SEQ ID NO. 26 (called LAH3), SEQ ID NO. 27/SEQ ID NO. 28 (called LAH5 herein), and combinations thereof. In other embodiments, the fully human single chain antibody has both a heavy chain variable domain region and a light chain variable domain region, wherein the single chain fully human antibody has a heavy chain/light chain variable domain sequence selected from the group consisting of SEQ ID NO. 1/SEQ ID NO. 2, SEQ ID NO. 3/SEQ ID NO. 4, SEQ ID NO. 5/SEQ ID NO. 6, SEQ ID NO. 7/SEQ ID NO. 8, SEQ ID NO. 9/SEQ ID NO. 10, SEQ ID NO. 11/SEQ ID NO. 12, SEQ ID NO. 13/SEQ ID NO. 14, SEQ ID NO. 15/SEQ ID NO. 16, SEQ ID NO. 17/SEQ ID NO. 18, SEQ ID NO. 19/SEQ ID NO. 20, SEQ ID NO. 21/SEQ ID NO. 22, SEQ ID NO. 23/SEQ ID NO. 24, SEQ ID NO. 25/SEQ ID NO. 26, SEQ ID NO. 27/SEQ ID NO. 28, and combinations thereof.

The present disclosure further provides a method for treating a broad spectrum of mammalian cancers, comprising an anti-CD123 polypeptide, e.g., an anti-human CD123 antibody, or antigen binding fragment thereof.

In certain embodiments, the broad spectrum of mammalian cancers to be treated is selected from the group consisting of non-Hodgkin's lymphoma (NHL), Burkitt's lymphoma (BL), multiple myeloma (MM), B chronic lymphocytic leukemia (B-CLL), B and T acute lymphocytic leukemia (ALL), T cell lymphoma (TCL), acute myeloid leukemia (ANIL), hairy cell leukemia (HCL), Hodgkin's Lymphoma (HL), and chronic myeloid leukemia (CML).

In certain embodiments, the anti-CD123 antibody, or antigen-binding fragment thereof, of the invention has a K_(D) of at least 1×10⁻⁶ M. In other embodiments, the anti-CD123 antibody, or antigen-binding fragment thereof, of the invention has a K_(D) of at least 1×10⁻⁷ M. In other embodiments, the anti-CD123 antibody, or antigen-binding fragment thereof, of the invention has a K_(D) of at least 1×10⁻⁸ M; at least 1×10⁻⁹ M, or at least 1×10⁻¹⁰ M.

In one embodiment, the anti-CD123 antibody is an IgG. In certain embodiments, the anti-CD123 antibody is an IgG1 isotype. In other embodiments, the anti-CD123 antibody is an IgG4 isotype.

In certain embodiments, the anti-CD123 antibody, or antigen-binding fragment, described herein is recombinant. In certain embodiments, the anti-CD123 antibody, or antigen-binding fragment, described herein is a human antibody, or antigen binding fragment of an antibody.

The invention also provides pharmaceutical compositions comprising an effective amount of an anti-CD123 antibodies or fragments disclosed herein, and a pharmaceutically acceptable carrier.

DESCRIPTION OF THE DRAWINGS

The data in FIG. 1 show that five of anti-CD123 antibodies tested bound and promoted ADCC activity against RPMI8226 target cells.

DETAILED DESCRIPTION Definitions

The terms “peptide,” “polypeptide” and “protein” each refers to a molecule comprising two or more amino acid residues joined to each other by peptide bonds. These terms encompass, e.g., native and artificial proteins, protein fragments and polypeptide analogs (such as muteins, variants, and fusion proteins) of a protein sequence as well as post-translationally, or otherwise covalently or non-covalently, modified proteins. A peptide, polypeptide, or protein may be monomeric or polymeric.

A “variant” of a polypeptide (for example, a variant of an antibody) comprises an amino acid sequence wherein one or more amino acid residues are inserted into, deleted from and/or substituted into the amino acid sequence relative to another polypeptide sequence. Disclosed variants include, for example, fusion proteins.

A “derivative” of a polypeptide is a polypeptide (e.g., an antibody) that has been chemically modified, e.g., via conjugation to another chemical moiety (such as, for example, polyethylene glycol or albumin, e.g., human serum albumin), phosphorylation, and glycosylation. Unless otherwise indicated, the term “antibody” includes, in addition to antibodies comprising two full-length heavy chains and two full-length light chains, derivatives, variants, fragments, and muteins thereof, examples of which are described below.

An “antigen binding protein” is a protein comprising a portion that binds to an antigen and, optionally, a scaffold or framework portion that allows the antigen binding portion to adopt a conformation that promotes binding of the antigen binding protein to the antigen. Examples of antigen binding proteins include antibodies, antibody fragments (e.g., an antigen binding portion of an antibody), antibody derivatives, and antibody analogs. The antigen binding protein can comprise, for example, an alternative protein scaffold or artificial scaffold with grafted CDRs or CDR derivatives. Such scaffolds include, but are not limited to, antibody-derived scaffolds comprising mutations introduced to, for example, stabilize the three-dimensional structure of the antigen binding protein as well as wholly synthetic scaffolds comprising, for example, a biocompatible polymer. See, for example, Korndorfer et al., 2003, Proteins: Structure, Function, and Bioinformatics, Volume 53, Issue 1:121-129; Roque et al., 2004, Biotechnol. Prog. 20:639-654. In addition, peptide antibody mimetics (“PAMs”) can be used, as well as scaffolds based on antibody mimetics utilizing fibronection components as a scaffold.

An antigen binding protein can have, for example, the structure of an immunoglobulin. An “immunoglobulin” is a tetrameric molecule composed of two identical pairs of polypeptide chains, each pair having one “light” (about 25 kDa) and one “heavy” chain (about 50-70 kDa). The amino-terminal portion of each chain includes a variable region of about 100 to 110 or more amino acids primarily responsible for antigen recognition. The carboxy-terminal portion of each chain defines a constant region primarily responsible for effector function. Human light chains are classified as kappa or lambda light chains. Heavy chains are classified as mu, delta, gamma, alpha, or epsilon, and define the antibody's isotype as IgM, IgD, IgG, IgA, and IgE, respectively. Preferably, the anti-CD123 antibodies disclosed herein are characterized by their variable domain region sequences in the heavy V_(H) and light V_(L) amino acid sequences. Within light and heavy chains, the variable and constant regions are joined by a “J” region of about 12 or more amino acids, with the heavy chain also including a “D” region of about 10 more amino acids. See generally, Fundamental Immunology Ch. 7 (Paul, W., ed., 2nd ed. Raven Press, N.Y. (1989)). The variable regions of each light/heavy chain pair form the antibody binding site such that an intact immunoglobulin has two binding sites.

The variable regions of immunoglobulin chains exhibit the same general structure of relatively conserved framework regions (FR) joined by three hypervariable regions, also called complementarity determining regions or CDRs. From N-terminus to C-terminus, both light and heavy chains comprise the domains FR1, CDR1, FR2, CDR2, FR3, CDR3 and FR4. The assignment of amino acids to each domain is in accordance with the definitions of Kabat et al. in Sequences of Proteins of Immunological Interest, 5^(th) Ed., US Dept. of Health and Human Services, PHS, NIH, NIH Publication no. 91-3242, 1991. Other numbering systems for the amino acids in immunoglobulin chains include IMGT® (international ImMunoGeneTics information system; Lefranc et al, Dev. Comp. Immunol. 29:185-203; 2005) and AHo (Honegger and Pluckthun, J. Mol. Biol. 309(3):657-670; 2001).

An “antibody” refers to an intact immunoglobulin or to an antigen binding portion thereof that competes with the intact antibody for specific binding, unless otherwise specified. In one embodiment, an antibody comprises two identical heavy chains each comprising a heavy chain variable domain and heavy chain constant regions C_(H1), C_(H2) and C_(H3); and comprises two identical light chains each comprising a light chain variable domain and a light chain constant region (C_(L)). In one embodiment, an antibody of the invention comprises a heavy and light chain variable domain sequence selected from those described herein in SEQ ID Nos: 1 to 28.

Antigen binding portions of an antibody may be produced by recombinant DNA techniques or by enzymatic or chemical cleavage of intact antibodies. Antigen binding portions include, inter alia, Fab, Fab′, F(ab′)₂, Fv, domain antibodies (dAbs), and complementarity determining region (CDR) fragments, single-chain antibodies (scFv), chimeric antibodies, diabodies, triabodies, tetrabodies, and polypeptides that contain at least a portion of an immunoglobulin that is sufficient to confer specific antigen binding to the polypeptide.

In certain embodiments, antibodies can be obtained from sources such as serum or plasma that contain immunoglobulins having varied antigenic specificity. If such antibodies are subjected to affinity purification, they can be enriched for a particular antigenic specificity. Such enriched preparations of antibodies usually are made of less than about 10% antibody having specific binding activity for the particular antigen. Subjecting these preparations to several rounds of affinity purification can increase the proportion of antibody having specific binding activity for the antigen. Antibodies prepared in this manner are often referred to as “monospecific.”

The term “monospecific”, as used herein, refers to an antibody that displays an affinity for one particular epitope. Monospecfic antibody preparations can be made up of about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 75%, 80%, 85%, 90%, 95%, 97%, 99%, or 99.9% antibody having specific binding activity for the particular antigen.

In certain embodiments, an antigen binding protein, such as an antibody, may have one or more binding sites. If there is more than one binding site, the binding sites may be identical to one another or may be different. For example, a naturally occurring human immunoglobulin typically has two identical binding sites, while a “bispecific” or “bifunctional” antibody has two different binding sites.

An “antibody fragment” or “antigen binding fragment of an antibody” comprises a portion of an intact antibody, and preferably comprises the antibody antigen binding or variable domains. Examples of an antibody fragment include, but not limited to, a Fab, a Fab′, an F(ab′)2, an Fv fragment, and a linear antibody. Antibody fragments are also referred to as “antibody portions” throughout.

Antigen binding portions (or fragments) of an antibody may be produced by recombinant DNA techniques or by enzymatic or chemical cleavage of intact antibodies. Antigen binding portions include, inter alia, Fab, Fab′, F(ab′)2, Fv, domain antibodies (dAbs), and complementarity determining region (CDR) fragments, single-chain antibodies (scFv), chimeric antibodies, diabodies, triabodies, tetrabodies, and polypeptides that contain at least a portion of an immunoglobulin that is sufficient to confer specific antigen binding to the polypeptide.

A Fab fragment is a monovalent fragment having the V_(L), V_(H), C_(L) and C_(H1) domains; a F(ab′)₂ fragment is a bivalent fragment having two Fab fragments linked by a disulfide bridge at the hinge region; a Fd fragment has the V_(H) and C_(H1) domains; an Fv fragment has the V_(L) and V_(H) domains of a single arm of an antibody; and a dAb fragment has a V_(H) domain, a V_(L) domain, or an antigen-binding fragment of a V_(H) or V_(L) domain (U.S. Pat. Nos. 6,846,634; 6,696,245, US App. Pub. 20/0202512; 2004/0202995; 2004/0038291; 2004/0009507; 20 03/0039958, and Ward et al., Nature 341:544-546, 1989).

A single-chain antibody (scFv) is an antibody in which a V_(L) and a V_(H) region are joined via a linker (e.g., a synthetic sequence of amino acid residues) to form a continuous protein chain wherein the linker is long enough to allow the protein chain to fold back on itself and form a monovalent antigen binding site (see, e.g., Bird et al., 1988, Science 242:423-26 and Huston et al., 1988, Proc. Natl. Acad. Sci. USA 85:5879-83).

Diabodies are bivalent antibodies comprising two polypeptide chains, wherein each polypeptide chain comprises V_(H) and V_(L) domains joined by a linker that is too short to allow for pairing between two domains on the same chain, thus allowing each domain to pair with a complementary domain on another polypeptide chain (see, e.g., Holliger et al., 1993, Proc. Natl. Acad. Sci. USA 90:6444-48, and Poljak et al., 1994, Structure 2:1121-23). If the two polypeptide chains of a diabody are identical, then a diabody resulting from their pairing will have two identical antigen binding sites. Polypeptide chains having different sequences can be used to make a diabody with two different antigen binding sites. Similarly, tribodies and tetrabodies are antibodies comprising three and four polypeptide chains, respectively, and forming three and four antigen binding sites, respectively, which can be the same or different.

The term “human antibody” includes antibodies that have one or more variable and constant regions derived from human immunoglobulin sequences. In one embodiment, all of the variable and constant domains of the antibody are derived from human immunoglobulin sequences (referred to as “a fully human antibody”). These antibodies may be prepared in a variety of ways, examples of which are described below, including through the immunization with an antigen of interest of a mouse that is genetically modified to express antibodies derived from human heavy and/or light chain-encoding genes. In a preferred embodiment, a fully human antibody is made using recombinant methods such that the glycosylation pattern of the antibody is different than an antibody having the same sequence if it were to exist in nature.

A “humanized antibody” has a sequence that differs from the sequence of an antibody derived from a non-human species by one or more amino acid substitutions, deletions, and/or additions, such that the humanized antibody is less likely to induce an immune response, and/or induces a less severe immune response, as compared to the non-human species antibody, when it is administered to a human subject. In one embodiment, certain amino acids in the framework and constant domains of the heavy and/or light chains of the non-human species antibody are mutated to produce the humanized antibody. In another embodiment, the constant domain(s) from a human antibody are fused to the variable domain(s) of a non-human species. In another embodiment, one or more amino acid residues in one or more CDR sequences of a non-human antibody are changed to reduce the likely immunogenicity of the non-human antibody when it is administered to a human subject, wherein the changed amino acid residues either are not critical for immunospecific binding of the antibody to its antigen, or the changes to the amino acid sequence that are made are conservative changes, such that the binding of the humanized antibody to the antigen is not significantly worse than the binding of the non-human antibody to the antigen. Examples of how to make humanized antibodies may be found in U.S. Pat. Nos. 6,054,297, 5,886,152 and 5,877,293.

The term “chimeric antibody” refers to an antibody that contains one or more regions from one antibody and one or more regions from one or more other antibodies. In one embodiment, one or more of the CDRs are derived from a human anti-CD123 antibody. In another embodiment, all of the CDRs are derived from a human anti-CD123 antibody. In another embodiment, the CDRs from more than one human anti-CD123 antibodies are mixed and matched in a chimeric antibody. For instance, a chimeric antibody may comprise a CDR1 from the light chain of a first human anti-PAR-2 antibody, a CDR2 and a CDR3 from the light chain of a second human anti-CD123 antibody, and the CDRs from the heavy chain from a third anti-CD123 antibody. Other combinations are possible.

Further, the framework regions may be derived from one of the same anti-CD123 antibodies, from one or more different antibodies, such as a human antibody, or from a humanized antibody. In one example of a chimeric antibody, a portion of the heavy and/or light chain is identical with, homologous to, or derived from an antibody from a particular species or belonging to a particular antibody class or subclass, while the remainder of the chain(s) is/are identical with, homologous to, or derived from an antibody (-ies) from another species or belonging to another antibody class or subclass. Also included are fragments of such antibodies that exhibit the desired biological activity (i.e., the ability to specifically bind CD123).

A “CDR grafted antibody” is an antibody comprising one or more CDRs derived from an antibody of a particular species or isotype and the framework of another antibody of the same or different species or isotype.

A “multi-specific antibody” is an antibody that recognizes more than one epitope on one or more antigens. A subclass of this type of antibody is a “bi-specific antibody” which recognizes two distinct epitopes on the same or different antigens.

An antigen binding protein “specifically binds” to an antigen (e.g., CD123) if it binds to the antigen with a dissociation constant of 1 nanomolar or less.

An “antigen binding domain, “antigen binding region,” or “antigen binding site” is a portion of an antigen binding protein that contains amino acid residues (or other moieties) that interact with an antigen and contribute to the antigen binding protein's specificity and affinity for the antigen. For an antibody that specifically binds to its antigen, this will include at least part of at least one of its CDR domains.

The term “Fc polypeptide” includes native and mutein forms of polypeptides derived from the Fc region of an antibody. Truncated forms of such polypeptides containing the hinge region that promotes dimerization also are included. Fusion proteins comprising Fc moieties (and oligomers formed therefrom) offer the advantage of facile purification by affinity chromatography over Protein A or Protein G columns.

An “epitope” is the portion of a molecule that is bound by an antigen binding protein (e.g., by an antibody). An epitope can comprise non-contiguous portions of the molecule (e.g., in a polypeptide, amino acid residues that are not contiguous in the polypeptide's primary sequence but that, in the context of the polypeptide's tertiary and quaternary structure, are near enough to each other to be bound by an antigen binding protein).

The “percent identity” or “percent homology” of two polynucleotide or two polypeptide sequences is determined by comparing the sequences using the GAP computer program (a part of the GCG Wisconsin Package, version 10.3 (Accelrys, San Diego, Calif.)) using its default parameters.

The terms “polynucleotide,” “oligonucleotide” and “nucleic acid” are used interchangeably throughout and include DNA molecules (e.g., cDNA or genomic DNA), RNA molecules (e.g., mRNA), analogs of the DNA or RNA generated using nucleotide analogs (e.g., peptide nucleic acids and non-naturally occurring nucleotide analogs), and hybrids thereof. The nucleic acid molecule can be single-stranded or double-stranded. In one embodiment, the nucleic acid molecules of the invention comprise a contiguous open reading frame encoding an antibody, or a fragment, derivative, mutein, or variant thereof.

Two single-stranded polynucleotides are “the complement” of each other if their sequences can be aligned in an anti-parallel orientation such that every nucleotide in one polynucleotide is opposite its complementary nucleotide in the other polynucleotide, without the introduction of gaps, and without unpaired nucleotides at the 5′ or the 3′ end of either sequence. A polynucleotide is “complementary” to another polynucleotide if the two polynucleotides can hybridize to one another under moderately stringent conditions. Thus, a polynucleotide can be complementary to another polynucleotide without being its complement.

A “vector” is a nucleic acid that can be used to introduce another nucleic acid linked to it into a cell. One type of vector is a “plasmid,” which refers to a linear or circular double stranded DNA molecule into which additional nucleic acid segments can be ligated. Another type of vector is a viral vector (e.g., replication defective retroviruses, adenoviruses and adeno-associated viruses), wherein additional DNA segments can be introduced into the viral genome. Certain vectors are capable of autonomous replication in a host cell into which they are introduced (e.g., bacterial vectors comprising a bacterial origin of replication and episomal mammalian vectors). Other vectors (e.g., non-episomal mammalian vectors) are integrated into the genome of a host cell upon introduction into the host cell, and thereby are replicated along with the host genome. An “expression vector” is a type of vector that can direct the expression of a chosen polynucleotide.

A nucleotide sequence is “operably linked” to a regulatory sequence if the regulatory sequence affects the expression (e.g., the level, timing, or location of expression) of the nucleotide sequence. A “regulatory sequence” is a nucleic acid that affects the expression (e.g., the level, timing, or location of expression) of a nucleic acid to which it is operably linked. The regulatory sequence can, for example, exert its effects directly on the regulated nucleic acid, or through the action of one or more other molecules (e.g., polypeptides that bind to the regulatory sequence and/or the nucleic acid). Examples of regulatory sequences include promoters, enhancers and other expression control elements (e.g., polyadenylation signals). Further examples of regulatory sequences are described in, for example, Goeddel, 1990, Gene Expression Technology: Methods in Enzymology 185, Academic Press, San Diego, Calif. and Baron et al., 1995, Nucleic Acids Res. 23:3605-06.

A “host cell” is a cell that can be used to express a nucleic acid, e.g., a nucleic acid of the invention. A host cell can be a prokaryote, for example, E. coli, or it can be a eukaryote, for example, a single-celled eukaryote (e.g., a yeast or other fungus), a plant cell (e.g., a tobacco or tomato plant cell), an animal cell (e.g., a human cell, a monkey cell, a hamster cell, a rat cell, a mouse cell, or an insect cell) or a hybridoma. Examples of host cells include the COS-7 line of monkey kidney cells (ATCC CRL 1651) (see Gluzman et al., 1981, Cell 23:175), L cells, C127 cells, 3T3 cells (ATCC CCL 163), Chinese hamster ovary (CHO) cells or their derivatives such as Veggie CHO and related cell lines which grow in serum-free media (see Rasmussen et al., 1998, Cytotechnology 28:31) or CHO strain DX-B11, which is deficient in DHFR (see Urlaub et al., 1980, Proc. Natl. Acad. Sci. USA 77:4216-20), HeLa cells, BHK (ATCC CRL 10) cell lines, the CV1/EBNA cell line derived from the African green monkey kidney cell line CV1 (ATCC CCL 70) (see McMahan et al., 1991, EMBO J. 10:2821), human embryonic kidney cells such as 293,293 EBNA or MSR 293, human epidermal A431 cells, human Colo205 cells, other transformed primate cell lines, normal diploid cells, cell strains derived from in vitro culture of primary tissue, primary explants, HL-60, U937, HaK or Jurkat cells. In one embodiment, a host cell is a mammalian host cell, but is not a human host cell. Typically, a host cell is a cultured cell that can be transformed or transfected with a polypeptide-encoding nucleic acid, which can then be expressed in the host cell. The phrase “recombinant host cell” can be used to denote a host cell that has been transformed or transfected with a nucleic acid to be expressed. A host cell also can be a cell that comprises the nucleic acid but does not express it at a desired level unless a regulatory sequence is introduced into the host cell such that it becomes operably linked with the nucleic acid. It is understood that the term host cell refers not only to the particular subject cell but also to the progeny or potential progeny of such a cell. Because certain modifications may occur in succeeding generations due to, e.g., mutation or environmental influence, such progeny may not, in fact, be identical to the parent cell, but are still included within the scope of the term as used herein.

The term “recombinant antibody” refers to an antibody that is prepared according to standard recombinant expression methods. A recombinant antibody can, for example, be expressed from a cell or cell line transfected with an expression vector (or possibly more than one expression vector) comprising the coding sequence of the antibody, where said coding sequence is not naturally associated with the cell. In one embodiment, a recombinant antibody has a glycosylation pattern that is different than the glycosylation pattern of an antibody having the same sequence if it were to exist in nature. In one embodiment, a recombinant antibody is expressed in a mammalian host cell which is not a human host cell. Notably, individual mammalian host cells have unique glycosylation patterns.

The term “effective amount” as used herein, refers to that amount of an antibody, or an antigen binding portion thereof that binds CD123, which is sufficient to effect treatment of a disease when administered to a subject. A therapeutically effective amount of an antibody, or fragment, provided herein will vary depending upon the relative activity of the antibodies and depending upon the subject and disease condition being treated, the weight and age of the subject, the severity of the disease condition, the manner of administration and the like, which can readily be determined by one of ordinary skill in the art.

The term “isolated” refers to a protein (e.g., an antibody) that is substantially free of other cellular material. In one embodiment, an isolated antibody is substantially free of other proteins from the same species. In one embodiment, an isolated antibody is expressed by a cell from a different species and is substantially free of other proteins from the different species. A protein may be rendered substantially free of naturally associated components (or components associated with the cellular expression system used to produce the antibody) by isolation, using protein purification techniques well known in the art. In one embodiment, the anti-CD123 antibodies, or antigen binding fragments, of the invention are isolated.

A “neutralizing antibody” or an “inhibitory antibody” is an antibody that inhibits the proteolytic activation of CD123 when an excess of the anti-CD123 antibody reduces the amount of activation by at least about 20% using an assay such as those described herein in the Examples. In various embodiments, the antigen binding protein reduces the amount of amount of proteolytic activation of CD123 by at least 30%, 40%, 50%, 60%, 70%, 75%, 80%, 85%, 90%, 95%, 97%, 99%, and 99.9%.

CD123 Antigen Binding Proteins

The present invention pertains to CD123 binding proteins, particularly anti-CD123 antibodies, or antigen-binding fragments thereof, (e.g., anti-CD123 human antibodies and antibody fragments) that bind CD123, e.g., human CD123, and uses thereof. Various aspects of the invention relate to antibodies and antibody fragments, pharmaceutical compositions, nucleic acids, recombinant expression vectors, and host cells for making such antibodies and fragments. Methods of using the antibodies of the invention to detect human CD123, to inhibit CD123 activity, either in vitro or in vivo, and to prevent or treat disorders such as cancer are also encompassed by the invention.

Included in the sequences listed are novel human antibody heavy and light chain variable regions that are specific to CD123. In one embodiment, the invention provides an anti-CD123 antibody, or an antigen-binding fragment thereof, that comprises a heavy chain having a variable domain comprising an amino acid sequence as set forth in SEQ ID NO.1, SEQ ID NO. 3, SEQ ID NO. 5, SEQ ID NO. 7, SEQ ID NO. 9, SEQ ID NO. 11, SEQ ID NO. 13, SEQ ID NO. 15, SEQ ID NO. 17, SEQ ID NO. 19, SEQ ID NO. 21, SEQ ID NO. 23, SEQ ID NO. 25 and SEQ ID NO. 27. In one embodiment, the invention provides an anti-CD123 antibody, or an antigen-binding fragment thereof, that comprises a light chain having a variable domain comprising an amino acid sequence as set forth in any one of SEQ ID Nos. 2, SEQ ID NO. 4, SEQ ID NO. 6, SEQ ID NO. 8, SEQ ID NO. 10, SEQ ID NO. 12, SEQ ID NO. 14, SEQ ID NO. 16, SEQ ID NO. 18, SEQ ID NO. 20, SEQ ID NO. 22, SEQ ID NO. 24, SEQ ID NO. 26 and SEQ ID NO. 28. In one embodiment, the invention provides an anti-CD123 antibody, or an antigen-binding fragment thereof, that comprises a light chain having a variable domain comprising an amino acid sequence as set forth in any one of SEQ ID Nos. 2, SEQ ID NO. 4, SEQ ID NO. 6, SEQ ID NO. 8, SEQ ID NO. 10, SEQ ID NO. 12, SEQ ID NO. 14, SEQ ID NO. 16, SEQ ID NO. 18, SEQ ID NO. 20, SEQ ID NO. 22, SEQ ID NO. 24, SEQ ID NO. 26 and SEQ ID NO. 28; and heavy chain having a variable domain comprising an amino acid sequence as set forth in any one of SEQ ID NO.1, SEQ ID NO. 3, SEQ ID NO. 5, SEQ ID NO. 7, SEQ ID NO. 9, SEQ ID NO. 11, SEQ ID NO. 13, SEQ ID NO. 15, SEQ ID NO. 17, SEQ ID NO. 19, SEQ ID NO. 21, SEQ ID NO. 23, SEQ ID NO. 25 and SEQ ID NO. 27.

Complementarity determining regions (CDRs) are known as hypervariable regions both in the light chain and the heavy chain variable domains. The more highly conserved portions of variable domains are called the framework (FR). Complementarity determining regions (CDRs) and framework regions (FR) of a given antibody may be identified using the system described by Kabat et al. supra; Lefranc et al., supra and/or Honegger and Pluckthun, supra. Also familiar to those in the art is the numbering system described in Kabat et al. (1991, NIH Publication 91-3242, National Technical Information Service, Springfield, Va.). In this regard Kabat et al. defined a numbering system for variable domain sequences that is applicable to any antibody. One of ordinary skill in the art can unambiguously assign this system of “Kabat numbering” to any variable domain amino acid sequence, without reliance on any experimental data beyond the sequence itself.

In certain embodiments, the present invention provides an anti-CD123 antibody comprising the CDRs of the heavy and light chain variable domains described in SEQ ID Nos: 1 to 28. For example, the invention provides an anti-CD123 antibody, or antigen-binding fragment thereof, comprising a heavy chain variable region having the CDRs described in an amino acid sequence as set forth in SEQ ID NO.1, SEQ ID NO. 3, SEQ ID NO. 5, SEQ ID NO. 7, SEQ ID NO. 9, SEQ ID NO. 11, SEQ ID NO. 13, SEQ ID NO. 15, SEQ ID NO. 17, SEQ ID NO. 19, SEQ ID NO. 21, SEQ ID NO. 23, SEQ ID NO. 25 and SEQ ID NO. 27. In one embodiment, the invention provides an anti-CD123 antibody, or antigen-binding fragment thereof, comprising a light chain variable region having CDRs described in an amino acid sequence as set forth in any one of SEQ ID Nos. 2, SEQ ID NO. 4, SEQ ID NO. 6, SEQ ID NO. 8, SEQ ID NO. 10, SEQ ID NO. 12, SEQ ID NO. 14, SEQ ID NO. 16, SEQ ID NO. 18, SEQ ID NO. 20, SEQ ID NO. 22, SEQ ID NO. 24, SEQ ID NO. 26 and SEQ ID NO. 28. In one embodiment, the invention provides an anti-CD123 antibody, or antigen-binding fragment thereof, comprising a light chain variable region having CDRs described in an amino acid sequence as set forth in any one of SEQ ID Nos. 2, SEQ ID NO. 4, SEQ ID NO. 6, SEQ ID NO. 8, SEQ ID NO. 10, SEQ ID NO. 12, SEQ ID NO. 14, SEQ ID NO. 16, SEQ ID NO. 18, SEQ ID NO. 20, SEQ ID NO. 22, SEQ ID NO. 24, SEQ ID NO. 26 and SEQ ID NO. 28; and a heavy chain variable region having CDRs described in an amino acid sequence as set forth in any one of SEQ ID NO.1, SEQ ID NO. 3, SEQ ID NO. 5, SEQ ID NO. 7, SEQ ID NO. 9, SEQ ID NO. 11, SEQ ID NO. 13, SEQ ID NO. 15, SEQ ID NO. 17, SEQ ID NO. 19, SEQ ID NO. 21, SEQ ID NO. 23, SEQ ID NO. 25 and SEQ ID NO. 27.

In one embodiment, the present disclosure provides a fully human antibody of an IgG class that binds to a CD123 epitope with a binding affinity of at least 10⁻⁶M, which has a heavy chain variable domain sequence that is at least 95% identical, at least 96% identical, at least 97% identical, at least 98% identical, or at least 99% identical, to the amino acid sequences selected from the group consisting of SEQ ID NO. 1, SEQ ID NO. 3, SEQ ID NO. 5, SEQ ID NO. 6, SEQ ID NO. 7, SEQ ID NO. 9, SEQ ID NO. 11, SEQ ID NO. 13, SEQ ID NO. 15, SEQ ID NO. 17, SEQ ID NO. 19, SEQ ID NO. 21, SEQ ID NO. 23, SEQ ID NO. 25, SEQ ID NO. 27, and combinations thereof, and that has a light chain variable domain sequence that is at least 95% identical, at least 96% identical, at least 97% identical, at least 98% identical, or at least 99% identical, to the amino acid sequence consisting of SEQ ID NO. 2, SEQ ID NO. 4, SEQ ID NO. 6, SEQ ID NO. 8, SEQ ID NO. 10, SEQ ID NO. 12, SEQ ID NO. 14, SEQ ID NO. 16, SEQ ID NO. 18, SEQ ID NO. 20, SEQ ID NO. 22, SEQ ID NO. 24, SEQ ID NO. 26, SEQ ID NO. 28, and combinations thereof.

In one embodiment, the fully human antibody has both a heavy chain and a light chain wherein the antibody has a heavy chain/light chain variable domain sequence selected from the group consisting SEQ ID NO. 1/SEQ ID NO. 2 (called LAA3 herein), SEQ ID NO. 3/SEQ ID NO. 4 (called LAA4 herein), SEQ ID NO. 5/SEQ ID NO. 6 (called LAA6 herein), SEQ ID NO. 7/SEQ ID NO. 8 (called LAA8 herein), SEQ ID NO. 9/SEQ ID NO. 10 (called LAB11 herein), SEQ ID NO. 11/SEQ ID NO. 12 (called LAB2 herein), SEQ ID NO. 13/SEQ ID NO. 14 (called LAC11 herein), SEQ ID NO. 15/SEQ ID NO. 16 (called LAC12 herein), SEQ ID NO. 17/SEQ ID NO. 18 (called LAE4 herein), SEQ ID NO. 19/SEQ ID NO. 20 (called LAF5 herein), SEQ ID NO. 21/SEQ ID NO. 22 (called LAF7 herein), SEQ ID NO. 23/SEQ ID NO. 24 (called LAG12 herein), SEQ ID NO. 25/SEQ ID NO. 26 (called LAH3), SEQ ID NO. 27/SEQ ID NO. 28 (called LAH5 herein), and combinations thereof.

In one embodiment, the substitutions made within a heavy or light chain that is at least 95% identical (or at least 96% identical, or at least 97% identical, or at least 98% identical, or at least 99% identical) are conservative amino acid substitutions. A “conservative amino acid substitution” is one in which an amino acid residue is substituted by another amino acid residue having a side chain (R group) with similar chemical properties (e.g., charge or hydrophobicity). In general, a conservative amino acid substitution will not substantially change the functional properties of a protein. In cases where two or more amino acid sequences differ from each other by conservative substitutions, the percent sequence identity or degree of similarity may be adjusted upwards to correct for the conservative nature of the substitution. Means for making this adjustment are well-known to those of skill in the art. See, e.g., Pearson (1994) Methods Mol. Biol. 24: 307-331, herein incorporated by reference. Examples of groups of amino acids that have side chains with similar chemical properties include (1) aliphatic side chains: glycine, alanine, valine, leucine and isoleucine; (2) aliphatic-hydroxyl side chains: serine and threonine; (3) amide-containing side chains: asparagine and glutamine; (4) aromatic side chains: phenylalanine, tyrosine, and tryptophan; (5) basic side chains: lysine, arginine, and histidine; (6) acidic side chains: aspartate and glutamate, and (7) sulfur-containing side chains are cysteine and methionine.

Antigen-binding fragments of antigen binding proteins of the invention may be produced by conventional techniques. Examples of such fragments include, but are not limited to, Fab and F(ab′)2 fragments.

In one embodiment, the present disclosure provides a Fab fully human antibody fragment, having a variable domain region from a heavy chain and a variable domain region from a light chain, wherein the heavy chain variable domain sequence that is at least 95% identical, at least 96% identical, at least 97% identical, at least 98% identical, or at least 99% identical, to the amino acid sequences selected from the group consisting of SEQ ID NO. 1, SEQ ID NO. 3, SEQ ID NO. 5, SEQ ID NO. 6, SEQ ID NO. 7, SEQ ID NO. 9, SEQ ID NO. 11, SEQ ID NO. 13, SEQ ID NO. 15, SEQ ID NO. 17, SEQ ID NO. 19, SEQ ID NO. 21, SEQ ID NO. 23, SEQ ID NO. 25, SEQ ID NO. 27, and combinations thereof, and that has a light chain variable domain sequence that is at least 95% identical, at least 96% identical, at least 97% identical, at least 98% identical, or at least 99% identical, to the amino acid sequence consisting of SEQ ID NO. 2, SEQ ID NO. 4, SEQ ID NO. 6, SEQ ID NO. 8, SEQ ID NO. 10, SEQ ID NO. 12, SEQ ID NO. 14, SEQ ID NO. 16, SEQ ID NO. 18, SEQ ID NO. 20, SEQ ID NO. 22, SEQ ID NO. 24, SEQ ID NO. 26, SEQ ID NO. 28, and combinations thereof.

In one embodiment, the fully human antibody Fab fragment has both a heavy chain variable domain region and a light chain variable domain region wherein the antibody has a heavy chain/light chain variable domain sequence selected from the group consisting SEQ ID NO. 1/SEQ ID NO. 2, SEQ ID NO. 3/SEQ ID NO. 4, SEQ ID NO. 5/SEQ ID NO. 6, SEQ ID NO. 7/SEQ ID NO. 8, SEQ ID NO. 9/SEQ ID NO. 10, SEQ ID NO. 11/SEQ ID NO. 12, SEQ ID NO. 13/SEQ ID NO. 14, SEQ ID NO. 15/SEQ ID NO. 16, SEQ ID NO. 17/SEQ ID NO. 18, SEQ ID NO. 19/SEQ ID NO. 20, SEQ ID NO. 21/SEQ ID NO. 22, SEQ ID NO. 23/SEQ ID NO. 24, SEQ ID NO. 25/SEQ ID NO. 26, SEQ ID NO. 27/SEQ ID NO. 28, and combinations thereof.

In one embodiment, the present disclosure provides a single chain human antibody, having a variable domain region from a heavy chain and a variable domain region from a light chain and a peptide linker connection the heavy chain and light chain variable domain regions, wherein the heavy chain variable domain sequence that is at least 95% identical, at least 96% identical, at least 97% identical, at least 98% identical, or at least 99% identical, to the amino acid sequences selected from the group consisting of SEQ ID NO. 1, SEQ ID NO. 3, SEQ ID NO. 5, SEQ ID NO. 6, SEQ ID NO. 7, SEQ ID NO. 9, SEQ ID NO. 11, SEQ ID NO. 13, SEQ ID NO. 15, SEQ ID NO. 17, SEQ ID NO. 19, SEQ ID NO. 21, SEQ ID NO. 23, SEQ ID NO. 25, SEQ ID NO. 27, and that has a light chain variable domain sequence that is at least 95% identical, at least 96% identical, at least 97% identical, at least 98% identical, or at least 99% identical, to the amino acid sequence consisting of SEQ ID NO. 2, SEQ ID NO. 4, SEQ ID NO. 6, SEQ ID NO. 8, SEQ ID NO. 10, SEQ ID NO. 12, SEQ ID NO. 14, SEQ ID NO. 16, SEQ ID NO. 18, SEQ ID NO. 20, SEQ ID NO. 22, SEQ ID NO. 24, SEQ ID NO. 26, SEQ ID NO. 28, and combinations thereof.

In one embodiment, the fully human single chain antibody has both a heavy chain variable domain region and a light chain variable domain region, wherein the single chain fully human antibody has a heavy chain/light chain variable domain sequence selected from the group consisting of SEQ ID NO. 1/SEQ ID NO. 2, SEQ ID NO. 3/SEQ ID NO. 4, SEQ ID NO. 5/SEQ ID NO. 6, SEQ ID NO. 7/SEQ ID NO. 8, SEQ ID NO. 9/SEQ ID NO. 10, SEQ ID NO. 11/SEQ ID NO. 12, SEQ ID NO. 13/SEQ ID NO. 14, SEQ ID NO. 15/SEQ ID NO. 16, SEQ ID NO. 17/SEQ ID NO. 18, SEQ ID NO. 19/SEQ ID NO. 20, SEQ ID NO. 21/SEQ ID NO. 22, SEQ ID NO. 23/SEQ ID NO. 24, SEQ ID NO. 25/SEQ ID NO. 26, SEQ ID NO. 27/SEQ ID NO. 28, and combinations thereof.

In one embodiment, the present disclosure further provides a method for treating a broad spectrum of mammalian cancers, comprising administering an anti-CD123 polypeptide, wherein the fully human antibody has a heavy chain variable domain sequence that is at least 95% identical, at least 96% identical, at least 97% identical, at least 98% identical, or at least 99% identical, to the amino acid sequences selected from the group consisting of SEQ ID NO. 1, SEQ ID NO. 3, SEQ ID NO. 5, SEQ ID NO. 6, SEQ ID NO. 7, SEQ ID NO. 9, SEQ ID NO. 11, SEQ ID NO. 13, SEQ ID NO. 15, SEQ ID NO. 17, SEQ ID NO. 19, SEQ ID NO. 21, SEQ ID NO. 23, SEQ ID NO. 25, SEQ ID NO. 27, and combinations thereof, and that has a light chain variable domain sequence that is at least 95% identical, at least 96% identical, at least 97% identical, at least 98% identical, or at least 99% identical, to the amino acid consisting of SEQ ID NO. 2, SEQ ID NO. 4, SEQ ID NO. 6, SEQ ID NO. 8, SEQ ID NO. 10, SEQ ID NO. 12, SEQ ID NO. 14, SEQ ID NO. 16, SEQ ID NO. 18, SEQ ID NO. 20, SEQ ID NO. 22, SEQ ID NO. 24, SEQ ID NO. 26, SEQ ID NO. 28, and combinations thereof;

wherein the Fab fully human antibody fragment has the heavy chain variable domain sequence that is at least 95% identical, at least 96% identical, at least 97% identical, at least 98% identical, or at least 99% identical, to the amino acid sequences selected from the group consisting of SEQ ID NO. 1, SEQ ID NO. 3, SEQ ID NO. 5, SEQ ID NO. 7, SEQ ID NO. 9, SEQ ID NO. 11, SEQ ID NO. 13, SEQ ID NO. 15, SEQ ID NO. 17, SEQ ID NO. 19, SEQ ID NO. 21, SEQ ID NO. 23, SEQ ID NO. 25, SEQ ID NO. 27, and combinations thereof, and that has the light chain variable domain sequence that is at least 95% identical, at least 96% identical, at least 97% identical, at least 98% identical, or at least 99% identical, to the amino acid sequence consisting of SEQ ID NO. 2, SEQ ID NO. 4, SEQ ID NO. 6, SEQ ID NO. 8, SEQ ID NO. 10, SEQ ID NO. 12, SEQ ID NO. 14, SEQ ID NO. 16, SEQ ID NO. 18, SEQ ID NO. 20, SEQ ID NO. 22, SEQ ID NO. 24, SEQ ID NO. 26, SEQ ID NO. 28, and combinations thereof; and

wherein the single chain human antibody has the heavy chain variable domain sequence that is at least 95% identical, at least 96% identical, at least 97% identical, at least 98% identical, or at least 99% identical, to the amino acid sequences selected from the group consisting of SEQ ID NO. 1, SEQ ID NO. 3, SEQ ID NO. 5, SEQ ID NO. 7, SEQ ID NO. 9, SEQ ID NO. 11, SEQ ID NO. 13, SEQ ID NO. 15, SEQ ID NO. 17, SEQ ID NO. 19, SEQ ID NO. 21, SEQ ID NO. 23, SEQ ID NO. 25, SEQ ID NO. 27, and combinations thereof, and that has the light chain variable domain sequence that is at least 95% identical, at least 96% identical, at least 97% identical, at least 98% identical, or at least 99% identical, to the amino acid sequence consisting of SEQ ID NO. 2, SEQ ID NO. 4, SEQ ID NO. 6, SEQ ID NO. 8, SEQ ID NO. 10, SEQ ID NO. 12, SEQ ID NO. 14, SEQ ID NO. 16, SEQ ID NO. 18, SEQ ID NO. 20, SEQ ID NO. 22, SEQ ID NO. 24, SEQ ID NO. 26, SEQ ID NO. 28, and combinations thereof.

Preferably, the fully human antibody has both a heavy chain and a light chain wherein the antibody has a heavy chain/light chain variable domain sequence selected from the group consisting of SEQ ID NO. 1/SEQ ID NO. 2 (called LAA3 herein), SEQ ID NO. 3/SEQ ID NO. 4 (called LAA4 herein), SEQ ID NO. 5/SEQ ID NO. 6 (called LAA6 herein), SEQ ID NO. 7/SEQ ID NO. 8 (called LAA8 herein), SEQ ID NO. 9/SEQ ID NO. 10 (called LAB11 herein), SEQ ID NO. 11/SEQ ID NO. 12 (called LAB2 herein), SEQ ID NO. 13/SEQ ID NO. 14 (called LAC11 herein), SEQ ID NO. 15/SEQ ID NO. 16 (called LAC12 herein), SEQ ID NO. 17/SEQ ID NO. 18 (called LAE4 herein), SEQ ID NO. 19/SEQ ID NO. 20 (called LAF5 herein), SEQ ID NO. 21/SEQ ID NO. 22 (called LAF7 herein), SEQ ID NO. 23/SEQ ID NO. 24 (called LAG12 herein), SEQ ID NO. 25/SEQ ID NO. 26 (called LAH3), SEQ ID NO. 27/SEQ ID NO. 28 (called LAH5 herein), and combinations thereof. Preferably, the fully human antibody Fab fragment has both a heavy chain variable domain region and a light chain variable domain region wherein the antibody has a heavy chain/light chain variable domain sequence selected from the group consisting of SEQ ID NO. 1/SEQ ID NO. 2 (called LAA3 herein), SEQ ID NO. 3/SEQ ID NO. 4 (called LAA4 herein), SEQ ID NO. 5/SEQ ID NO. 6 (called LAA6 herein), SEQ ID NO. 7/SEQ ID NO. 8 (called LAA8 herein), SEQ ID NO. 9/SEQ ID NO. 10 (called LAB11 herein), SEQ ID NO. 11/SEQ ID NO. 12 (called LAB2 herein), SEQ ID NO. 13/SEQ ID NO. 14 (called LAC11 herein), SEQ ID NO. 15/SEQ ID NO. 16 (called LAC12 herein), SEQ ID NO. 17/SEQ ID NO. 18 (called LAE4 herein), SEQ ID NO. 19/SEQ ID NO. 20 (called LAF5 herein), SEQ ID NO. 21/SEQ ID NO. 22 (called LAF7 herein), SEQ ID NO. 23/SEQ ID NO. 24 (called LAG12 herein), SEQ ID NO. 25/SEQ ID NO. 26 (called LAH3), SEQ ID NO. 27/SEQ ID NO. 28 (called LAH5 herein), and combinations thereof. Preferably, the fully human single chain antibody has both a heavy chain variable domain region and a light chain variable domain region, wherein the single chain fully human antibody has a heavy chain/light chain variable domain sequence selected from the group consisting of SEQ ID NO. 1/SEQ ID NO. 2, SEQ ID NO. 3/SEQ ID NO. 4, SEQ ID NO. 5/SEQ ID NO. 6, SEQ ID NO. 7/SEQ ID NO. 8, SEQ ID NO. 9/SEQ ID NO. 10, SEQ ID NO. 11/SEQ ID NO. 12, SEQ ID NO. 13/SEQ ID NO. 14, SEQ ID NO. 15/SEQ ID NO. 16, SEQ ID NO. 17/SEQ ID NO. 18, SEQ ID NO. 19/SEQ ID NO. 20, SEQ ID NO. 21/SEQ ID NO. 22, SEQ ID NO. 23/SEQ ID NO. 24, SEQ ID NO. 25/SEQ ID NO. 26, SEQ ID NO. 27/SEQ ID NO. 28, and combinations thereof.

Techniques are known for deriving an antibody of a different subclass or isotype from an antibody of interest, i.e., subclass switching. Thus, IgG antibodies may be derived from an IgM antibody, for example, and vice versa. Such techniques allow the preparation of new antibodies that possess the antigen-binding properties of a given antibody (the parent antibody), but also exhibit biological properties associated with an antibody isotype or subclass different from that of the parent antibody. Recombinant DNA techniques may be employed. Cloned DNA encoding particular antibody polypeptides may be employed in such procedures, e.g., DNA encoding the constant domain of an antibody of the desired isotype (Lantto et al., 2002, Methods Mol. Biol. 178:303-16). Moreover, if an IgG4 is desired, it may also be desired to introduce a point mutation (CPSCP→CPPCP) in the hinge region (Bloom et al., 1997, Protein Science 6:407) to alleviate a tendency to form intra-H chain disulfide bonds that can lead to heterogeneity in the IgG4 antibodies. Thus, in one embodiment, the antibody of the invention is a human IgG1 antibody. Thus, in one embodiment, the antibody of the invention is a human IgG4 antibody.

The present disclosure provides a number of antibodies structurally characterized by the amino acid sequences of their variable domain regions. However, the amino acid sequences can undergo some changes while retaining their high degree of binding to their specific targets. More specifically, many amino acids in the variable domain region can be changed with conservative substitutions and it is predictable that the binding characteristics of the resulting antibody will not differ from the binding characteristics of the wild type antibody sequence. There are many amino acids in an antibody variable domain that do not directly interact with the antigen or impact antigen binding and are not critical for determining antibody structure. For example, a predicted nonessential amino acid residue in any of the disclosed antibodies is preferably replaced with another amino acid residue from the same class. Methods of identifying amino acid conservative substitutions which do not eliminate antigen binding are well-known in the an (see, e.g., Brummell et al., Biochem. 32: 1180-1187 (1993); Kobayashi et al. Protein Eng. 12(10):879-884 (1999); and Burks et al. Proc. Natl. Acad. Sci. USA 94:412-417 (1997)). Near et al. Mol. Immunol. 30:369-377, 1993 explains how to impact or not impact binding through site-directed mutagenesis. Near et al. only mutated residues that they thought had a high probability of changing antigen binding. Most had a modest or negative effect on binding affinity (Near et al. Table 3) and binding to different forms of digoxin (Near et al. Table 2). Thus, the present disclosure also includes variable sequences having at least 95% identity, at least 96% identity, at least 97% identity, at least 98% identity, or at least 99% identity to those sequences disclosed herein.

In certain embodiments, an antibody, or antigen-binding fragment thereof, provided herein has a dissociation constant (K_(D)) of 1×10⁻⁶ M or less; 5×10⁻⁷ M or less' 1×10⁻⁷ M or less; 5×10⁻⁸ M or less; 1×10⁻⁸ M or less; 5×10⁻⁹ M or less; or 1×10⁻⁹ M or less. In one embodiment, the antibody, or antigen-binding fragment thereof, of the invention as a K_(D) from 1×10⁻⁷ M to 1×10⁻¹⁰ M. In one embodiment, the antibody, or antigen-binding fragment thereof, of the invention as a K_(D) from 1×10⁻⁸ M to 1×10⁻¹⁰ M.

Those of ordinary skill in the art will appreciate methods known for determining the K_(D) of an antibody, or fragment thereof. For example, in one embodiment, K_(D) is measured by a radiolabeled antigen binding assay (RIA). In one embodiment, an RIA is performed with the Fab version of an antibody of interest and its antigen. For example, solution binding affinity of Fabs for antigen is measured by equilibrating Fab with a minimal concentration of (¹²⁵I)-labeled antigen in the presence of a titration series of unlabeled antigen, then capturing bound antigen with an anti-Fab antibody-coated plate (see, e.g., Chen et al., J. Mol. Biol. 293:865-881(1999)). According to another embodiment, K_(D) is measured using a BIACORE surface plasmon resonance assay. The term “surface plasmon resonance”, as used herein, refers to an optical phenomenon that allows for the analysis of real-time interactions by detection of alterations in protein concentrations within a biosensor matrix, for example using the BIACORE system (Biacore Life Sciences division of GE Healthcare, Piscataway, N.J.).

In another aspect, the present disclosure provides an antigen binding protein that inhibits an activity of CD123. In one embodiment, the antigen binding protein has an IC₅₀ of 1000 nM or lower. In another embodiment, the IC₅₀ is 100 nM or lower; in another embodiment, the IC₅₀ is 10 nM or lower. In another embodiment, the IC₅₀ is substantially the same as that of an antibody described herein in the Examples. In another embodiment, the antigen binding protein inhibits an activity of CD123 with substantially the same IC₅₀ as an antibody described herein.

In another aspect, the present disclosure provides an antigen binding protein that binds to human CD123 expressed on the surface of a cell and, when so bound, inhibits CD123 signaling activity in the cell without causing a significant reduction in the amount of CD123 on the surface of the cell. Any method for determining or estimating the amount of CD123 on the surface and/or in the interior of the cell can be used. In other embodiments, binding of the antigen binding protein to the CD123-expressing cell causes less than about 75%, 50%, 40%, 30%, 20%, 15%, 10%, 5%, 1%, or 0.1% of the cell-surface CD123 to be internalized.

In another aspect, the present disclosure provides an antigen binding protein having a half-life of at least one day in vitro or in vivo (e.g., when administered to a human subject). In one embodiment, the antigen binding protein has a half-life of at least three days. In another embodiment, the antigen binding protein has a half-life of four days or longer. In another embodiment, the antigen binding protein has a half-life of eight days or longer. In another embodiment, the antigen binding protein is derivatized or modified such that it has a longer half-life as compared to the underivatized or unmodified antigen binding protein. In another embodiment, the antigen binding protein contains one or more point mutations to increase serum half-life, such as described in WO2000/09560.

The present disclosure further provides multi-specific antigen binding proteins, for example, bispecific antigen binding protein, e.g., antigen binding protein that bind to two different epitopes of CD123, or to an epitope of CD123 and an epitope of another molecule, via two different antigen binding sites or regions. Moreover, bispecific antigen binding protein as disclosed herein can comprise a CD123 binding site from one of the herein-described antibodies and a second CD123 binding region from another of the herein-described antibodies, including those described herein by reference to other publications. Alternatively, a bispecific antigen binding protein may comprise an antigen binding site from one of the herein described antibodies and a second antigen binding site from another CD123 antibody that is known in the art, or from an antibody that is prepared by known methods or the methods described herein.

Numerous methods of preparing bispecific antibodies are known in the art. Such methods include the use of hybrid-hybridomas as described by Milstein et al., 1983, Nature 305:537, and chemical coupling of antibody fragments (Brennan et al., 1985, Science 229:81; Glennie et al., 1987, J. Immunol. 139:2367; U.S. Pat. No. 6,010,902). Moreover, bispecific antibodies can be produced via recombinant means, for example by using leucine zipper moieties (i.e., from the Fos and Jun proteins, which preferentially form heterodimers; Kostelny et al., 1992, J. Immunol. 148:1547) or other lock and key interactive domain structures as described in U.S. Pat. No. 5,582,996. Additional useful techniques include those described in U.S. Pat. Nos. 5,959,083; and 5,807,706.

In another aspect, the antigen binding protein comprises a derivative of an antibody. The derivatized antibody can comprise any molecule or substance that imparts a desired property to the antibody, such as increased half-life in a particular use. The derivatized antibody can comprise, for example, a detectable (or labeling) moiety (e.g., a radioactive, colorimetric, antigenic or enzymatic molecule, a detectable bead (such as a magnetic or electrodense (e.g., gold) bead), or a molecule that binds to another molecule (e.g., biotin or streptavidin), a therapeutic or diagnostic moiety (e.g., a radioactive, cytotoxic, or pharmaceutically active moiety), or a molecule that increases the suitability of the antibody for a particular use (e.g., administration to a subject, such as a human subject, or other in vivo or in vitro uses). Examples of molecules that can be used to derivatize an antibody include albumin (e.g., human serum albumin) and polyethylene glycol (PEG). Albumin-linked and PEGylated derivatives of antibodies can be prepared using techniques well known in the art. In one embodiment, the antibody is conjugated or otherwise linked to transthyretin (TTR) or a TTR variant. The TTR or TTR variant can be chemically modified with, for example, a chemical selected from the group consisting of dextran, poly(n-vinyl pyurrolidone), polyethylene glycols, propropylene glycol homopolymers, polypropylene oxide/ethylene oxide co-polymers, polyoxyethylated polyols and polyvinyl alcohols.

Oligomers that contain one or more antigen binding proteins may be employed as CD123 antagonists. Oligomers may be in the form of covalently-linked or non-covalently-linked dimers, trimers, or higher oligomers. Oligomers comprising two or more antigen binding protein are contemplated for use, with one example being a homodimer. Other oligomers include heterodimers, homotrimers, heterotrimers, homotetramers, heterotetramers, etc.

One embodiment is directed to oligomers comprising multiple antigen binding proteins joined via covalent or non-covalent interactions between peptide moieties fused to the antigen binding proteins. Such peptides may be peptide linkers (spacers), or peptides that have the property of promoting oligomerization. Leucine zippers and certain polypeptides derived from antibodies are among the peptides that can promote oligomerization of antigen binding proteins attached thereto, as described in more detail below.

In particular embodiments, the oligomers comprise from two to four antigen binding proteins. The antigen binding proteins of the oligomer may be in any form, such as any of the forms described above, e.g., variants or fragments. Preferably, the oligomers comprise antigen binding proteins that have CD123 binding activity.

Another method for preparing oligomeric antigen binding proteins involves use of a leucine zipper. Leucine zipper domains are peptides that promote oligomerization of the proteins in which they are found. Leucine zippers were originally identified in several DNA-binding proteins (Landschulz et al., 1988, Science 240:1759), and have since been found in a variety of different proteins. Among the known leucine zippers are naturally occurring peptides and derivatives thereof that dimerize or trimerize. Examples of leucine zipper domains suitable for producing soluble oligomeric proteins are described in WO 94/10308, and the leucine zipper derived from lung surfactant protein D (SPD) described in Hoppe et al., 1994, FEBS Letters 344:191. The use of a modified leucine zipper that allows for stable trimerization of a heterologous protein fused thereto is described in Fanslow et al., 1994, Semin. Immunol. 6:267-78. In one approach, recombinant fusion proteins comprising an anti-CD123 antibody fragment or derivative fused to a leucine zipper peptide are expressed in suitable host cells, and the soluble oligomeric anti-CD123 antibody fragments or derivatives that form are recovered from the culture supernatant.

Antigen binding proteins directed against CD123 can be used, for example, in assays to detect the presence of CD123 polypeptides, either in vitro or in vivo. The antigen binding proteins also may be employed in purifying CD123 proteins by immunoaffinity chromatography. Blocking antigen binding proteins can be used in the methods disclosed herein. Such antigen binding proteins that function as CD123 antagonists may be employed in treating any CD123-induced condition, including but not limited to various cancers.

Antigen binding proteins may be employed in an in vitro procedure, or administered in vivo to inhibit CD123-induced biological activity. Disorders that would benefit (directly or indirectly) from activation of CD123, examples of which are provided herein, thus may be treated. In one embodiment, the present invention provides a therapeutic method comprising in vivo administration of a CD123 blocking antigen binding protein to a mammal in need thereof in an amount effective for reducing a CD123-induced biological activity.

In certain embodiments, antigen binding proteins include fully human monoclonal antibodies that inhibit a biological activity of CD123.

Antigen binding proteins, including antibodies and antibody fragments described herein, may be prepared by any of a number of conventional techniques. For example, they may be purified from cells that naturally express them (e.g., an antibody can be purified from a hybridoma that produces it), or produced in recombinant expression systems, using any technique known in the art. See, for example, Monoclonal Antibodies, Hybridomas: A New Dimension in Biological Analyses, Kennet et al. (eds.), Plenum Press, New York (1980); and Antibodies: A Laboratory Manual, Harlow and Land (eds.), Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y., (1988).

Any expression system known in the art can be used to make the recombinant polypeptides, including antibodies and antibody fragments described herein, of the invention. In general, host cells are transformed with a recombinant expression vector that comprises DNA encoding a desired polypeptide. Among the host cells that may be employed are prokaryotes, yeast or higher eukaryotic cells. Prokaryotes include gram negative or gram positive organisms, for example E. coli or bacilli. Higher eukaryotic cells include insect cells and established cell lines of mammalian origin. Examples of suitable mammalian host cell lines include the COS-7 line of monkey kidney cells (ATCC CRL 1651) (Gluzman et al., 1981, Cell 23:175), L cells, 293 cells, C127 cells, 3T3 cells (ATCC CCL 163), Chinese hamster ovary (CHO) cells, HeLa cells, BHK (ATCC CRL 10) cell lines, and the CV1/EBNA cell line derived from the African green monkey kidney cell line CV1 (ATCC CCL 70) as described by McMahan et al., 1991, EMBO J. 10: 2821. Appropriate cloning and expression vectors for use with bacterial, fungal, yeast, and mammalian cellular hosts are described by Pouwels et al. (Cloning Vectors: A Laboratory Manual, Elsevier, N.Y., 1985).

The transformed cells can be cultured under conditions that promote expression of the polypeptide, and the polypeptide recovered by conventional protein purification procedures. One such purification procedure includes the use of affinity chromatography, e.g., over a matrix having all or a portion (e.g., the extracellular domain) of CD123 bound thereto. Polypeptides contemplated for use herein include substantially homogeneous recombinant mammalian anti-CD123 antibody polypeptides substantially free of contaminating endogenous materials.

Antigen binding proteins may be prepared, and screened for desired properties, by any of a number of known techniques. Certain of the techniques involve isolating a nucleic acid encoding a polypeptide chain (or portion thereof) of an antigen binding protein of interest (e.g., an anti-CD123 antibody), and manipulating the nucleic acid through recombinant DNA technology. The nucleic acid may be fused to another nucleic acid of interest, or altered (e.g., by mutagenesis or other conventional techniques) to add, delete, or substitute one or more amino acid residues, for example.

Polypeptides of the present disclosure can be produced using any standard methods known in the art. In one example, the polypeptides are produced by recombinant DNA methods by inserting a nucleic acid sequence (a cDNA) encoding the polypeptide into a recombinant expression vector and expressing the DNA sequence under conditions promoting expression.

In one embodiment, the invention features nucleic acids encoding the antibodies or antibody fragments described herein. For example, in one embodiment, the invention includes a nucleic acid encoding a heavy chain variable domain as set forth in SEQ ID NO. 1, SEQ ID NO. 3, SEQ ID NO. 5, SEQ ID NO. 7, SEQ ID NO. 9, SEQ ID NO. 11, SEQ ID NO. 13, SEQ ID NO. 15, SEQ ID NO. 17, SEQ ID NO. 19, SEQ ID NO. 21, SEQ ID NO. 23, SEQ ID NO. 25, and SEQ ID NO. 27, and encoding a light chain variable domain as set forth in SEQ ID NO. 2, SEQ ID NO. 4, SEQ ID NO. 6, SEQ ID NO. 8, SEQ ID NO. 10, SEQ ID NO. 12, SEQ ID NO. 14, SEQ ID NO. 16, SEQ ID NO. 18, SEQ ID NO. 20, SEQ ID NO. 22, SEQ ID NO. 24, SEQ ID NO. 26, and SEQ ID NO. 28.

Nucleic acids encoding any of the various polypeptides disclosed herein may be synthesized chemically. Codon usage may be selected so as to improve expression in a cell. Such codon usage will depend on the cell type selected. Specialized codon usage patterns have been developed for E. coli and other bacteria, as well as mammalian cells, plant cells, yeast cells and insect cells.

General techniques for nucleic acid manipulation are described for example in Sambrook et al., Molecular Cloning: A Laboratory Manual, Vols. 1-3, Cold Spring Harbor Laboratory Press, 2 ed., 1989, or F. Ausubel et al., Current Protocols in Molecular Biology (Green Publishing and Wiley-Interscience: New York, 1987) and periodic updates, herein incorporated by reference. The DNA encoding the polypeptide is operably linked to suitable transcriptional or translational regulatory elements derived from mammalian, viral, or insect genes. Such regulatory elements include a transcriptional promoter, an optional operator sequence to control transcription, a sequence encoding suitable mRNA ribosomal binding sites, and sequences that control the termination of transcription and translation. The ability to replicate in a host, usually conferred by an origin of replication, and a selection gene to facilitate recognition of transformants is additionally incorporated.

The recombinant DNA can also include any type of protein tag sequence that may be useful for purifying the protein. Examples of protein tags include but are not limited to a histidine tag, a FLAG tag, a myc tag, an HA tag, or a GST tag. Appropriate cloning and expression vectors for use with bacterial, fungal, yeast, and mammalian cellular hosts can be found in Cloning Vectors: A Laboratory Manual, (Elsevier, N.Y., 1985).

The expression construct is introduced into the host cell using a method appropriate to the host cell. A variety of methods for introducing nucleic acids into host cells are known in the art, including, but not limited to, electroporation; transfection employing calcium chloride, rubidium chloride, calcium phosphate, DEAE-dextran, or other substances; microprojectile bombardment; lipofection; and infection (where the vector is an infectious agent). Suitable host cells include prokaryotes, yeast, mammalian cells, or bacterial cells.

Suitable bacteria include gram negative or gram positive organisms, for example, E. coli or Bacillus spp. Yeast, preferably from the Saccharomyces species, such as S. cerevisiae, may also be used for production of polypeptides. Various mammalian or insect cell culture systems can also be employed to express recombinant proteins. Baculovirus systems for production of heterologous proteins in insect cells are reviewed by Luckow and Summers, (Bio/Technology, 6:47, 1988). Examples of suitable mammalian host cell lines include endothelial cells, COS-7 monkey kidney cells, CV-1, L cells, C127, 3T3, Chinese hamster ovary (CHO), human embryonic kidney cells, HeLa, 293, 293T, and BHK cell lines. Purified polypeptides are prepared by culturing suitable host/vector systems to express the recombinant proteins. For many applications, the small size of many of the polypeptides disclosed herein would make expression in E. coli as the preferred method for expression. The protein is then purified from culture media or cell extracts.

Proteins can also be produced using cell-translation systems. For such purposes the nucleic acids encoding the polypeptide must be modified to allow in vitro transcription to produce mRNA and to allow cell-free translation of the mRNA in the particular cell-free system being utilized (eukaryotic such as a mammalian or yeast cell-free translation system or prokaryotic such as a bacterial cell-free translation system.

CD123-binding polypeptides can also be produced by chemical synthesis (such as by the methods described in Solid Phase Peptide Synthesis, 2nd ed., 1984, The Pierce Chemical Co., Rockford, Ill.). Modifications to the protein can also be produced by chemical synthesis.

The polypeptides of the present disclosure can be purified by isolation/purification methods for proteins generally known in the field of protein chemistry. Non-limiting examples include extraction, recrystallization, salting out (e.g., with ammonium sulfate or sodium sulfate), centrifugation, dialysis, ultrafiltration, adsorption chromatography, ion exchange chromatography, hydrophobic chromatography, normal phase chromatography, reversed-phase chromatography, gel filtration, gel permeation chromatography, affinity chromatography, electrophoresis, countercurrent distribution or any combinations of these. After purification, polypeptides may be exchanged into different buffers and/or concentrated by any of a variety of methods known to the art, including, but not limited to, filtration and dialysis.

The purified polypeptide is preferably at least 85% pure, more preferably at least 95% pure, and most preferably at least 98% pure. Regardless of the exact numerical value of the purity, the polypeptide is sufficiently pure for use as a pharmaceutical product.

In certain embodiments, the present disclosure provides monoclonal antibodies that bind to CD123. Monoclonal antibodies may be produced using any technique known in the art, e.g., by immortalizing spleen cells harvested from the transgenic animal after completion of the immunization schedule. The spleen cells can be immortalized using any technique known in the art, e.g., by fusing them with myeloma cells to produce hybridomas. Myeloma cells for use in hybridoma-producing fusion procedures preferably are non-antibody-producing, have high fusion efficiency, and enzyme deficiencies that render them incapable of growing in certain selective media which support the growth of only the desired fused cells (hybridomas). Examples of suitable cell lines for use in mouse fusions include Sp-20, P3-X63/Ag8, P3-X63-Ag8.653, NS1/1.Ag 41, Sp210-Ag14, FO, NSO/U, MPC-11, MPC11-X45-GTG 1.7 and S194/5XX0 Bul; examples of cell lines used in rat fusions include R210.RCY3, Y3-Ag 1.2.3, IR983F and 48210. Other cell lines useful for cell fusions are U-266, GM1500-GRG2, LICR-LON-HMy2 and UC729-6.

Antigen-binding fragments of antigen binding proteins of the invention may be produced by conventional techniques known in the art.

Post-Translational Modifications of Polypeptides

In certain embodiments, the binding polypeptides of the invention may further comprise post-translational modifications. Exemplary post-translational protein modifications include phosphorylation, acetylation, methylation, ADP-ribosylation, ubiquitination, glycosylation, carbonylation, sumoylation, biotinylation or addition of a polypeptide side chain or of a hydrophobic group. As a result, the modified soluble polypeptides may contain non-amino acid elements, such as lipids, poly- or mono-saccharide, and phosphates. A preferred form of glycosylation is sialylation, which conjugates one or more sialic acid moieties to the polypeptide. Sialic acid moieties improve solubility and serum half-life while also reducing the possible immunogeneticity of the protein. See Raju et al. Biochemistry. 2001 31; 40(30):8868-76.

In one embodiment, modified forms of the subject soluble polypeptides comprise linking the subject soluble polypeptides to nonproteinaceous polymers. In one embodiment, the polymer is polyethylene glycol (“PEG”), polypropylene glycol, or polyoxyalkylenes, in the manner as set forth in U.S. Pat. Nos. 4,640,835; 4,496,689; 4,301,144; 4,670,417; 4,791,192 or 4,179,337.

PEG is a water soluble polymer that is commercially available or can be prepared by ring-opening polymerization of ethylene glycol according to methods well known in the art (Sandler and Karo, Polymer Synthesis, Academic Press, New York, Vol. 3, pages 138-161). The term “PEG” is used broadly to encompass any polyethylene glycol molecule, without regard to size or to modification at an end of the PEG, and can be represented by the formula: X—O(CH₂CH₂O)_(n)—CH₂CH₂OH (1), where n is 20 to 2300 and X is H or a terminal modification, e.g., a C₁₋₄ alkyl. In one embodiment, the PEG of the invention terminates on one end with hydroxy or methoxy, i.e., X is H or CH₃ (“methoxy PEG”). A PEG can contain further chemical groups which are necessary for binding reactions; which results from the chemical synthesis of the molecule; or which is a spacer for optimal distance of parts of the molecule. In addition, such a PEG can consist of one or more PEG side-chains which are linked together. PEGs with more than one PEG chain are called multiarmed or branched PEGs. Branched PEGs can be prepared, for example, by the addition of polyethylene oxide to various polyols, including glycerol, pentaerythriol, and sorbitol. For example, a four-armed branched PEG can be prepared from pentaerythriol and ethylene oxide. Branched PEG are described in, for example, EP-A 0 473 084 and U.S. Pat. No. 5,932,462. One form of PEGs includes two PEG side-chains (PEG2) linked via the primary amino groups of a lysine (Monfardini et al., Bioconjugate Chem. 6 (1995) 62-69).

The serum clearance rate of PEG-modified polypeptide may be decreased by about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or even 90%, relative to the clearance rate of the unmodified binding polypeptide. The PEG-modified polypeptide may have a half-life (t_(1/2)) which is enhanced relative to the half-life of the unmodified protein. The half-life of PEG-binding polypeptide may be enhanced by at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 125%, 150%, 175%, 200%, 250%, 300%, 400% or 500%, or even by 1000% relative to the half-life of the unmodified binding polypeptide. In some embodiments, the protein half-life is determined in vitro, such as in a buffered saline solution or in serum. In other embodiments, the protein half-life is an in vivo half-life, such as the half-life of the protein in the serum or other bodily fluid of an animal.

Therapeutic Methods, Formulations and Modes of Administration

The present disclosure further provides methods for treating a broad spectrum of mammalian cancers, comprising administering anti-CD123 antibodies or antigen binding fragments of the present invention.

In one embodiment, the present disclosure provides a method for treating cancer comprising administering an anti-CD123 antibody, or fragment thereof, selected from the group consisting of a fully human antibody of an IgG class that binds to a CD123 epitope with a binding affinity of at least 10⁻⁶M; a Fab fully human antibody fragment comprising a variable domain from a heavy chain and a variable domain from a light chain; a single chain human antibody, comprising a variable domain from a heavy chain and a variable domain from a light chain and a peptide linker connecting the heavy chain and light chain variable domains. The heavy and light chain variable regions (and CDRs within said sequences) that may be used in the antibodies and fragments of the invention are described in SEQ ID Nos. 1-28.

In one embodiment, the methods described herein include the use of a fully human Fab antibody fragment comprising a heavy chain variable domain sequence that is at least 95% identical, at least 96% identical, at least 97% identical, at least 98% identical, or at least 99% identical, to an amino acid sequence selected from the group consisting of SEQ ID NO. 1, SEQ ID NO. 3, SEQ ID NO. 5, SEQ ID NO. 7, SEQ ID NO. 9, SEQ ID NO. 11, SEQ ID NO. 13, SEQ ID NO. 15, SEQ ID NO. 17, SEQ ID NO. 19, SEQ ID NO. 21, SEQ ID NO. 23, SEQ ID NO. 25, SEQ ID NO. 27, and combinations thereof, and that comprises a light chain variable domain sequence that is at least 95% identical, at least 96% identical, at least 97% identical, at least 98% identical, or at least 99% identical, to an amino acid sequence selected from the group consisting of SEQ ID NO. 2, SEQ ID NO. 4, SEQ ID NO. 6, SEQ ID NO. 8, SEQ ID NO. 10, SEQ ID NO. 12, SEQ ID NO. 14, SEQ ID NO. 16, SEQ ID NO. 18, SEQ ID NO. 20, SEQ ID NO. 22, SEQ ID NO. 24, SEQ ID NO. 26, SEQ ID NO. 28, and combinations thereof.

In one embodiment, the methods described herein include the use of a single chain human antibody comprising a heavy chain variable domain sequence that is at least 95% identical, at least 96% identical, at least 97% identical, at least 98% identical, or at least 99% identical, to an amino acid sequence selected from the group consisting of SEQ ID NO. 1, SEQ ID NO. 3, SEQ ID NO. 5, SEQ ID NO. 7, SEQ ID NO. 9, SEQ ID NO. 11, SEQ ID NO. 13, SEQ ID NO. 15, SEQ ID NO. 17, SEQ ID NO. 19, SEQ ID NO. 21, SEQ ID NO. 23, SEQ ID NO. 25, SEQ ID NO. 27, and combinations thereof, and that comprises a light chain variable domain sequence that is at least 95% identical, at least 96% identical, at least 97% identical, at least 98% identical, or at least 99% identical, to an amino acid sequence selected from the group consisting of SEQ ID NO. 2, SEQ ID NO. 4, SEQ ID NO. 6, SEQ ID NO. 8, SEQ ID NO. 10, SEQ ID NO. 12, SEQ ID NO. 14, SEQ ID NO. 16, SEQ ID NO. 18, SEQ ID NO. 20, SEQ ID NO. 22, SEQ ID NO. 24, SEQ ID NO. 26, SEQ ID NO. 28, and combinations thereof.

In one embodiment, the fully human antibody has both a heavy chain and a light chain wherein the antibody comprises a heavy chain/light chain variable domain sequence selected from the group consisting of SEQ ID NO. 1/SEQ ID NO. 2 (called LAA3 herein), SEQ ID NO. 3/SEQ ID NO. 4 (called LAA4 herein), SEQ ID NO. 5/SEQ ID NO. 6 (called LAA6 herein), SEQ ID NO. 7/SEQ ID NO. 8 (called LAA8 herein), SEQ ID NO. 9/SEQ ID NO. 10 (called LAB11 herein), SEQ ID NO. 11/SEQ ID NO. 12 (called LAB2 herein), SEQ ID NO. 13/SEQ ID NO. 14 (called LAC11 herein), SEQ ID NO. 15/SEQ ID NO. 16 (called LAC12 herein), SEQ ID NO. 17/SEQ ID NO. 18 (called LAE4 herein), SEQ ID NO. 19/SEQ ID NO. 20 (called LAF5 herein), SEQ ID NO. 21/SEQ ID NO. 22 (called LAF7 herein), SEQ ID NO. 23/SEQ ID NO. 24 (called LAG12 herein), SEQ ID NO. 25/SEQ ID NO. 26 (called LAH3 herein), SEQ ID NO. 27/SEQ ID NO. 28 (called LAH5 herein), SEQ ID NO. 29/SEQ ID NO. 30 (called herein), and combinations thereof. Preferably, the fully human antibody Fab fragment has both a heavy chain variable domain region and a light chain variable domain region wherein the antibody has a heavy chain/light chain variable domain sequence selected from the group consisting of SEQ ID NO. 1/SEQ ID NO. 2 (called LAA3 herein), SEQ ID NO. 3/SEQ ID NO. 4 (called LAA4 herein), SEQ ID NO. 5/SEQ ID NO. 6 (called LAA6 herein), SEQ ID NO. 7/SEQ ID NO. 8 (called LAA8 herein), SEQ ID NO. 9/SEQ ID NO. 10 (called LAB11 herein), SEQ ID NO. 11/SEQ ID NO. 12 (called LAB2 herein), SEQ ID NO. 13/SEQ ID NO. 14 (called LAC11 herein), SEQ ID NO. 15/SEQ ID NO. 16 (called LAC12 herein), SEQ ID NO. 17/SEQ ID NO. 18 (called LAE4 herein), SEQ ID NO. 19/SEQ ID NO. 20 (called LAF5 herein), SEQ ID NO. 21/SEQ ID NO. 22 (called LAF7 herein), SEQ ID NO. 23/SEQ ID NO. 24 (called LAG12 herein), SEQ ID NO. 25/SEQ ID NO. 26 (called LAH3 herein), SEQ ID NO. 27/SEQ ID NO. 28 (called LAH5 herein), SEQ ID NO. 29/SEQ ID NO. 30 (called herein), and combinations thereof.

In one embodiment, the fully human single chain antibody comprises both a heavy chain variable domain region and a light chain variable domain region, wherein the single chain fully human antibody comprises a heavy chain/light chain variable domain sequence selected from the group consisting of SEQ ID NO. 1/SEQ ID NO. 2, SEQ ID NO. 3/SEQ ID NO. 4, SEQ ID NO. 5/SEQ ID NO. 6, SEQ ID NO. 7/SEQ ID NO. 8, SEQ ID NO. 9/SEQ ID NO. 10, SEQ ID NO. 11/SEQ ID NO. 12, SEQ ID NO. 13/SEQ ID NO. 14, SEQ ID NO. 15/SEQ ID NO. 16, SEQ ID NO. 17/SEQ ID NO. 18, SEQ ID NO. 19/SEQ ID NO. 20, SEQ ID NO. 21/SEQ ID NO. 22, SEQ ID NO. 23/SEQ ID NO. 24, SEQ ID NO. 25/SEQ ID NO. 26, SEQ ID NO. 27/SEQ ID NO. 28, and combinations thereof.

Techniques and dosages for administration vary depending on the type of specific polypeptide and the specific condition being treated but can be readily determined by the skilled artisan. In general, regulatory agencies require that a protein reagent to be used as a therapeutic is formulated so as to have acceptably low levels of pyrogens. Accordingly, therapeutic formulations will generally be distinguished from other formulations in that they are substantially pyrogen free, or at least contain no more than acceptable levels of pyrogen as determined by the appropriate regulatory agency (e.g., FDA).

Therapeutic compositions of the present disclosure may be administered with a pharmaceutically acceptable diluent, carrier, or excipient, in unit dosage form. Administration may be parenteral (e.g., intravenous, subcutaneous), oral, or topical, as non-limiting examples. In addition, any gene therapy technique, using nucleic acids encoding the polypeptides of the invention, may be employed, such as naked DNA delivery, recombinant genes and vectors, cell-based delivery, including ex vivo manipulation of patients' cells, and the like.

The composition can be in the form of a pill, tablet, capsule, liquid, or sustained release tablet for oral administration; or a liquid for intravenous, subcutaneous or parenteral administration; gel, lotion, ointment, cream, or a polymer or other sustained release vehicle for local administration.

In certain embodiments, the disclosed antibodies are administered by inhalation, but aerosolization of full IgG antibodies may prove limiting due to their molecular size (˜150 kDa). To maximize available commercial aerosolization devices, smaller Fab fragments may be required.

Methods well known in the art for making formulations are found, for example, in “Remington: The Science and Practice of Pharmacy” (20th ed., ed. A. R. Gennaro A R., 2000, Lippincott Williams & Wilkins, Philadelphia, Pa.). Formulations for parenteral administration may, for example, contain excipients, sterile water, saline, polyalkylene glycols such as polyethylene glycol, oils of vegetable origin, or hydrogenated napthalenes. Biocompatible, biodegradable lactide polymer, lactide/glycolide copolymer, or polyoxyethylene-polyoxypropylene copolymers may be used to control the release of the compounds. Nanoparticulate formulations (e.g., biodegradable nanoparticles, solid lipid nanoparticles, liposomes) may be used to control the biodistribution of the compounds. Other potentially useful parenteral delivery systems include ethylene-vinyl acetate copolymer particles, osmotic pumps, implantable infusion systems, and liposomes. The concentration of the compound in the formulation varies depending upon a number of factors, including the dosage of the drug to be administered, and the route of administration.

The polypeptide may be optionally administered as a pharmaceutically acceptable salt, such as non-toxic acid addition salts or metal complexes that are commonly used in the pharmaceutical industry. Examples of acid addition salts include organic acids such as acetic, lactic, pamoic, maleic, citric, malic, ascorbic, succinic, benzoic, palmitic, suberic, salicylic, tartaric, methanesulfonic, toluenesulfonic, or trifluoroacetic acids or the like; polymeric acids such as tannic acid, carboxymethyl cellulose, or the like; and inorganic acid such as hydrochloric acid, hydrobromic acid, sulfuric acid phosphoric acid, or the like. Metal complexes include zinc, iron, and the like. In one example, the polypeptide is formulated in the presence of sodium acetate to increase thermal stability.

Formulations for oral use include tablets containing the active ingredient(s) in a mixture with non-toxic pharmaceutically acceptable excipients. These excipients may be, for example, inert diluents or fillers (e.g., sucrose and sorbitol), lubricating agents, glidants, and anti-adhesives (e.g., magnesium stearate, zinc stearate, stearic acid, silicas, hydrogenated vegetable oils, or talc).

Formulations for oral use may also be provided as chewable tablets, or as hard gelatin capsules wherein the active ingredient is mixed with an inert solid diluent, or as soft gelatin capsules wherein the active ingredient is mixed with water or an oil medium.

A therapeutically effective dose refers to a dose that produces the therapeutic effects for which it is administered. The exact dose will depend on the disorder to be treated, and may be ascertained by one skilled in the art using known techniques. In general, the polypeptide is administered at about 0.01 μg/kg to about 50 mg/kg per day, preferably 0.01 mg/kg to about 30 mg/kg per day, most preferably 0.1 mg/kg to about 20 mg/kg per day. The polypeptide may be given daily (e.g., once, twice, three times, or four times daily) or preferably less frequently (e.g., weekly, every two weeks, every three weeks, monthly, or quarterly). In addition, as is known in the art, adjustments for age as well as the body weight, general health, sex, diet, time of administration, drug interaction, and the severity of the disease may be necessary, and will be ascertainable with routine experimentation by those skilled in the art.

A CD123 binding polypeptide can be administered alone or in combination with one or more additional therapies such as chemotherapy radiotherapy, immunotherapy, surgical intervention, or any combination of these. Long-term therapy is equally possible as is adjuvant therapy in the context of other treatment strategies, as described above.

In certain embodiments of such methods, one or more polypeptide therapeutic agents can be administered, together (simultaneously) or at different times (sequentially). In addition, polypeptide therapeutic agents can be administered with another type of compounds for treating cancer or for inhibiting angiogenesis.

In certain embodiments, the subject anti-CD123 antibodies agents of the invention can be used alone.

In certain embodiments, the binding polypeptides of fragments thereof can be labeled or unlabeled for diagnostic purposes. Typically, diagnostic assays entail detecting the formation of a complex resulting from the binding of a binding polypeptide to CD123. The binding polypeptides or fragments can be directly labeled, similar to antibodies. A variety of labels can be employed, including, but not limited to, radionuclides, fluorescers, enzymes, enzyme substrates, enzyme cofactors, enzyme inhibitors and ligands (e.g., biotin, haptens). Numerous appropriate immunoassays are known to the skilled artisan (see, for example, U.S. Pat. Nos. 3,817,827; 3,850,752; 3,901,654; and 4,098,876). When unlabeled, the binding polypeptides can be used in assays, such as agglutination assays. Unlabeled binding polypeptides can also be used in combination with another (one or more) suitable reagent which can be used to detect the binding polypeptide, such as a labeled antibody reactive with the binding polypeptide or other suitable reagent (e.g., labeled protein A).

In one embodiment, the binding polypeptides of the present invention can be utilized in enzyme immunoassays, wherein the subject polypeptides are conjugated to an enzyme. When a biological sample comprising a CD123 protein is combined with the subject binding polypeptides, binding occurs between the binding polypeptides and the CD123 protein. In one embodiment, a sample containing cells expressing a CD123 protein (e.g., endothelial cells) is combined with the subject antibodies, and binding occurs between the binding polypeptides and cells bearing a CD123 protein recognized by the binding polypeptide. These bound cells can be separated from unbound reagents and the presence of the binding polypeptide-enzyme conjugate specifically bound to the cells can be determined, for example, by contacting the sample with a substrate of the enzyme which produces a color or other detectable change when acted on by the enzyme. In another embodiment, the subject binding polypeptides can be unlabeled, and a second, labeled polypeptide (e.g., an antibody) can be added which recognizes the subject binding polypeptide.

In certain aspects, kits for use in detecting the presence of a CD123 protein in a biological sample can also be prepared. Such kits will include a CD123 binding polypeptide which binds to a CD123 protein or portion of said receptor, as well as one or more ancillary reagents suitable for detecting the presence of a complex between the binding polypeptide and the receptor protein or portions thereof. The polypeptide compositions of the present invention can be provided in lyophilized form, either alone or in combination with additional antibodies specific for other epitopes. The binding polypeptides and/or antibodies, which can be labeled or unlabeled, can be included in the kits with adjunct ingredients (e.g., buffers, such as Tris, phosphate and carbonate, stabilizers, excipients, biocides and/or inert proteins, e.g., bovine serum albumin). For example, the binding polypeptides and/or antibodies can be provided as a lyophilized mixture with the adjunct ingredients, or the adjunct ingredients can be separately provided for combination by the user. Generally, the adjunct materials will be present in less than about 5% weight based on the amount of active binding polypeptide or antibody, and usually will be present in a total amount of at least about 0.001% weight based on polypeptide or antibody concentration. Where a second antibody capable of binding to the binding polypeptide is employed, such antibody can be provided in the kit, for instance in a separate vial or container. The second antibody, if present, is typically labeled, and can be formulated in an analogous manner with the antibody formulations described above.

Polypeptide sequences are indicated using standard one- or three-letter abbreviations. Unless otherwise indicated, each polypeptide sequence has amino termini at the left and a carboxy termini at the right; each single-stranded nucleic acid sequence, and the top strand of each double-stranded nucleic acid sequence, has a 5′ termini at the left and a 3′ termini at the right. A particular polypeptide sequence also can be described by explaining how it differs from a reference sequence.

Preferably, the broad spectrum of mammalian cancers to be treated is selected from the group consisting of non-Hodgkin's lymphoma (NHL), Burkitt's lymphoma (BL), multiple myeloma (MM), B chronic lymphocytic leukemia (B-CLL), B and T acute lymphocytic leukemia (ALL), T cell lymphoma (TCL), acute myeloid leukemia (AML), hairy cell leukemia (HCL), Hodgkin's Lymphoma (HL), and chronic myeloid leukemia (CML).

The CD123 antibodies described herein are useful in treating, delaying the progression of, preventing relapse of or alleviating a symptom of a cancer or other neoplastic condition, including, hematological malignancies and/or CD123+ tumors. The CD123 antibodies described herein are useful in treating a cancer selected from the group consisting of non-Hodgkin's lymphoma (NHL), acute lymphocytic leukemia (ALL), acute myeloid leukemia (AML), chronic lymphocytic leukemia (CLL), chronic myelogenous leukemia (CML), multiple myeloma (MM), breast cancer, ovarian cancer, head and neck cancer, bladder cancer, melanoma, colorectal cancer, pancreatic cancer, lung cancer, leiomyoma, leiomyosarcoma, glioma, glioblastoma, and solid tumors, wherein solid tumors are selected from the group consisting of breast tumors, ovarian tumors, lung tumors, pancreatic tumors, prostate tumors, melanoma tumors, colorectal tumors, lung tumors, head and neck tumors, bladder tumors, esophageal tumors, liver tumors, and kidney tumors.

As used herein, “hematological cancer” refers to a cancer of the blood, and includes leukemia, lymphoma and myeloma among others. “Leukemia” refers to a cancer of the blood in which too many white blood cells that are ineffective in fighting infection are made, thus crowding out the other parts that make up the blood, such as platelets and red blood cells. It is understood that cases of leukemia are classified as acute or chronic.

Certain forms of leukemia include, acute lymphocytic leukemia (ALL); acute myeloid leukemia (AML); chronic lymphocytic leukemia (CLL); chronic myelogenous leukemia (CML); Myeloproliferative disorder/neoplasm (MPDS); and myelodysplasia syndrome. “Lymphoma” may refer to a Hodgkin's lymphoma, both indolent and aggressive non-Hodgkin's lymphoma, Burkitt's lymphoma, and follicular lymphoma (small cell and large cell), among others. Myeloma may refer to multiple myeloma (MM), giant cell myeloma, heavy-chain myeloma, and light chain or Bence-Jones myeloma.

Example 1

The ability of anti-CD123 antibodies to bind to CD123 expressing cells and promote functional activity was determined using an ADCC assay. Effector cells for this assay were purified NK cells that had been incubated overnight in the presence of IL-2 (100 U/ml). Target cells were RPMI8226 cells, a myeloma cell line, which were added to wells at 5×10³ per well. Test antibodies were then added at 1 microgram per ml and incubated with the RPMI8226 cells for 20 minutes at 37° C. After washing, the effector cells were added at 1×10⁵ per well resulting in an effector to target ratio of 20:1. The assay was allowed to proceed for at least 4 hours after which time cytotoxicity was evaluated using a Promega Cyto-glo kit. The data in FIG. 1 show that five of anti-CD123 antibodies tested bound and promoted ADCC activity against RPMI8226 target cells.

Sequence Listing Heavy chain variable  Light chain domain region variable domain region LAA3 EVQLVESGGGLVKPGGSLRLSC QLTQPPSVSAAPGQKVTISCSGSNSNI AASGFTFSSYSMNWVRQAPGKG GNNYVSWYQQLPGTAPKLLIYDNNRR LEWVSSISSSSSYIYYADSVKGRF PSGIPDRFSGSKSGTSATLGITGLQTG TISRDNSKNTLYLQMNSLRAEDT DEADYFCGTWDSSLSAGVFGGGTKLT AVYYCARAEWFSEALDYVVGQGT VL SEQ ID NO. 2 LVTVSS SEQ ID NO. 1 LAA4 QVQLVQSGGGLVKPGGSLRLSC QSVVTQPPSVSAAPGQKVTISCSGSG AASGFTFSSYSMNWVRQAPGKG SNIGNNYVSWYQQLPGTAPKLLIYDNN LEWVSSISSSSSYIYYADSVKGRF KRPSGIPDRFSGSKSGTSATLGITGLQ TISRDNAKNSLYLQMNSLRPEDT TGDEADYYCATWDSSLSAPWVFGGG AVYYCARESGSDALDIWGRGTM TKVTVL SEQ ID NO. 4 VTVSS SEQ ID NO. 3 LAA6 EVQLVESGGGLVQPGGSLRLSC NFMLTQPASVSGSPGQSITISCTGTSA AASGFTFSSYEMNWVRQAPGKG DVGGDYYVSWYQQHPGKAPKLTIYDV LEWVSSISSSSSYIYYADSVKGRF SERPSGVSNRFSGSKSGNTASLTISGL TISRDNAKNSLYLQMNSLRAEDT QTEDEADYYCGSYTSSGTWLFGGGT AVYYCARADYYEAFDIWGQGTM KLTVL SEQ ID NO. 6 VTVSS SEQ ID NO. 5 LAA8 EVQLVESGGGLVKPGGSLRLSC QSALTQPPSVSVAPGQTARITCGGNNI AASGFTFSSYSMNWVRQAPGKG GSKSVHWYQQKPGQAPVLVVYDDSD LEWVSSISSSSSYIYYADSVKGRF RPSGIPERFSGSNSGNTATLTISRVEA TISRDNAKNSLYLQMNSLRAEDT GDEADYYCQVWDSSSDHLVFGGGTK AVYYCARAGTRGDAFDIWGQGT VTVL SEQ ID NO. 8 MVTVSS SEQ ID NO. 7 LAB11 QVQLVQSGAEVKKPGASVKVSC QLVLTQPPSVSAAPGQKVTISCSGSSS KASGYTFTSYGISWVRQAPGQG NIGNNYVSWYQQLPGTAPKLLIYDNNK LEWMGWISAYNGNTKYSQKLRG RPSGIPDRFSGSKSGTSATLGITGLQT RVTMTRDTSTSTAYMELRSLRSD GDEADYYCGTWDSSLSAVFGGGTKL DTAVYYCARDEEYDFWSGYGS TVL SEQ ID NO. 10 WYYYYGMDVWGQGTTVTVSS SEQ ID NO. 9 LAB2 EVQLVDSGGGLVKPGGSLRLSC QAGLTQPPSVSAAPGQQFTISCSGSS AASGFTFSSYSMNWVRQAPGKG SNIGKNYVSWYQQLPGSAPKLLIYDNH LEWVSSISSSSSYIYYADSVKGRF KRPSGIPDRFSGSKSGTSATLGITGLQ TISRDNAKNSLYLQMNSLRAEDT TGDEADYYCGTWDDSLSGWVFGGGT AVYYCAREDYYDSIDYWGQGTL KLTVL SEQ ID NO. 12 VTVSS SEQ ID NO. 11 LAC11 EVQLVESGGGLVQPGGSLRLSC QAGLTQPPSASGTPGQRVTIACSGSS AASGFTFSSYEMNWVRQAPGKG SNIGTYTVNWYQHVPGTAPKLLIYSTY LEWVSYISSSGSTIYYADSVKGR QRPLEVPDRFSGSKSGTSASLAISGLR FTISRDNAKNSLYLQMNSLRAED SEDEGDYYCASWDDRLNGFYVFGSG TAVYYCARVQQWPDDAFDIWGQ TKVTVL SEQ ID NO. 14 GTMVTVSS SEQ ID NO. 13 LAC12 EVQLVQSGGGVVQPGRSLRVSC QSVLTQPRSVSGSPGQSVTISCTGTSI AASGFTFSSYGMHWVRQTPGKG DVDKDNLVSWYQQHPGRVPKLIIYDV LEWVAGIWYDENDKYYADSVKG NKRPSGVPDHFSGSKSGTSASLAISG RFTISRDNSKNTLHLQMNSLRAE LRSEDEADYYCAAWDDSLSSWVFGG DTAVYYCARQFRDYYFDVWGRG GTKVTVL SEQ ID NO. 16 TLVTVSS SEQ ID NO. 15 LAE4 EVQLVQSGGGLVKPGGSLRLSC LPVLTQPASVSGSPGQSITISCTGTSS AASGFTFSNAWMSWVRQAPGK DVGRYDYVSWYQQHPGKAPQLMIYD GLEWVGRIKSKTDGGTTDYAAPV VSNRPSGVSNRFSGSKSGNTASLTIS KGRFTISRDDSKNTLYLQMNSLK GLQAEDEADYYCSSYTGSSTLYVFGT TEDTAVYYCTTDYDFWSGYYYW GTKVTVL SEQ ID NO. 18 GQGTTVTVSS SEQ ID NO. 17 LAF5 EVQLVQSGAEVKKPGSSVKVSC EVQLVQSGAEVKKPGSSVKVSCKASG KASGGTFSTYAISWVRQAPGQG GTFSTYAISWVRQAPGQGLEWMGGTI LEWMGGTIPKFGTANYAQKFQG PKFGTANYAQKFQGRVTITADESTSTA RVTITADESTSTAYMELSSLRSED YMELSSLRSEDTAVYYCARAVVPAAIV TAVYYCARAVVPAAIVEAMDVW EAMDVWGQGTTVTVSS SEQ ID NO. GQGTTVTVSS SEQ ID NO. 19 20 LAF7 QVQLVQSGAEVKKPGASVKVSC QAVLTQPPSVSVAPGKTARITCGGNNI KASGYTLSMYGISWVRHAPGQG GSKSVHWYQQKPGQAPVLVVYDDSD LEWMGWINPYTGDRKYAQRFQG RPSGIPERFSGSNSGNTATLTISRVEA RLTVTTDTSTATSYMELTSLRSD GDEADYYCQVWDSSSDHVVFGGGPQ DTAVYYCAREEYHDSMIGYYVG LTVL SEQ ID NO. 22 GFDLWGQGTLVTVSSSEQID NO. 21 LAG12 EVQLLESGGGLVKPGGSLRLSCA QSVLTQPPSVSAAPGHEVTISCSGSS ASGFTFSSYSMNWVRQAPGKGL SNIGNNYVSWYQQVPGTAPKLLIYDN EWVSSISSSSSYIYYADSVKGRF NKRASEIPDRFFGSKSGTSATLGVSGL TISRDNAKNSLYLQMNSLRAEDT QTGDEADYYCGTWDSSLNDVVFGGG AVYYCARANWDAFDIWGQGTMV TKLTVL SEQ ID NO. 24 TVSS SEQ ID NO. 23 LAH3 EVQLVESGGGLVKPGGSLRLSC LPVLTQSASVSGSPGQSITISCTGTSS AASGFTFSNAWMSWVRQAPGK DVGRYDYVSWYQQHPGKAPQLMIYD GLEWVGRIKSKTDGGTTDYAAPV VSNRPSGVSNRFSGSKSGNTASLTIS KGRFTISRDDSKNTLYLQMNSLK GLQAEDEADYYCSSYTGSSTLYVFGT TEDTAVYYCTTDYDFWSGYYYW GTKVTVL SEQ ID NO. 26 GQGTLVTVSS SEQ ID NO. 25 LAH5 EVQLVQSGAEVKKPGASVKVSC DIQLTQSPSSLSASVGDRVTITCRASQ KASGYTFTGYYMHWVRQAPGQ SISDYLNWYHQKPGKAPRLLIYAASSL GLEWMGWISAYNGNTNYAQKLQ QSGVPSRFSGTRSGTDFTLTINNLQPE GRVTMTTDTSTSTAYMELRSLRS DSATYYCQQSYSTPLTFGGGTKVDIK DDTAVYYCAREEDYYGSGEHYY SEQ ID NO. 28 FDYWGQGTLVTVSS SEQ ID NO. 27 

We claim:
 1. A recombinant anti-CD123 antibody, or an antigen-binding fragment thereof, that binds to CD123, comprising heavy chain variable domain and light chain variable domain amino acid sequences comprising all of the complementarity determining regions (CDRs) as set forth in a heavy and light chain variable domain amino acid sequences of either SEQ ID NO. 9 and SEQ ID NO. 10, or SEQ ID NO. 15 and SEQ ID NO. 16, respectively.
 2. The recombinant fully human anti-CD123 antibody of claim 1, wherein the antibody comprises heavy chain and light chain variable domain sequences of either SEQ ID NO. 9 and SEQ ID NO. 10, or SEQ ID NO. 15 and SEQ ID NO. 16, respectively.
 3. A method for treating a CD123 positive cancer in a human subject in need thereof, the method comprising the step of administering an effective amount of the recombinant fully human anti-CD123 antibody of claim 2, such that the cancer is treated.
 4. The method of claim 3, wherein the recombinant fully human anti CD123 antibody comprises heavy chain and light chain variable domain sequences of SEQ ID NO. 9 and SEQ ID NO.
 10. 5. The method of claim 3, wherein the recombinant fully human anti-CD123 antibody comprises heavy chain and light chain variable domain sequences of SEQ ID NO. 15 and SEQ ID NO.
 16. 6. The method of claim 3, wherein the cancer is selected from the group consisting of non-Hodgkin's lymphoma, Burkitt's lymphoma, multiple myeloma, B chronic lymphocytic leukemia, B and T acute lymphocyticleukemia, T cell lymphoma, acute myeloid leukemia, hairy cell leukemia, Hodgkin's Lymphoma, and chronic myeloid leukemia.
 7. The recombinant fully human anti-CD123 antibody of claim 2, wherein the antibody has a dissociation constant (K_(D)) of at least 1×10⁻⁶M.
 8. The recombinant fully human anti-CD123 antibody of claim 2, wherein the antibody is classified as an IgG isotype.
 9. The recombinant fully human anti-CD123 antibody of claim 8, wherein the antibody is an IgG1 or an IgG4.
 10. The recombinant anti-CD123 antibody, or antigen-binding fragment thereof, of claim 1, wherein antibody, or antigen-binding fragment is selected from the group consisting of a Fab, a Fab′, a F(ab′)2, an Fv, a single chain antibody, a chimeric antibody, a diabody, a triabody, and a tetrabody.
 11. The recombinant anti-CD123 antigen-binding fragment of claim 1, which is a single chain antibody.
 12. The recombinant anti-CD123 antibody, or antigen-binding fragment thereof, of claim 1, which has a K_(D) of at least 1×10⁻⁶M.
 13. A pharmaceutical composition comprising the recombinant anti-CD123 antibody, or antigen-binding fragment thereof, of claim 1, and a pharmaceutically acceptable carrier.
 14. The recombinant anti-CD123 antibody, or antigen-binding fragment thereof, of claim 1, wherein the antibody, or antigen-binding fragment thereof, is classified as an IgG isotype.
 15. The recombinant anti-CD123 antibody, or antigen-binding fragment thereof, of claim 14, wherein the antibody, or antigen-binding fragment thereof, is an IgG1 or an IgG4.
 16. A method of treating a CD123 positive cancer in a human subject in need thereof, said method comprising the step of administering an effective amount of the recombinant anti-CD123 antibody, or antigen-binding fragment thereof, of claim 1 to the subject, such that the cancer is treated.
 17. The method of claim 16, wherein the cancer is selected from the group consisting of non-Hodgkin's lymphoma, Burkitt's lymphoma, multiple myeloma, B chronic lymphocytic leukemia, B and T acute lymphocytic leukemia, T cell lymphoma, acute myeloid leukemia, hairy cell leukemia, Hodgkin's Lymphoma, and chronic myeloid leukemia.
 18. A recombinant fully human anti-CD123 antibody fragment that binds to CD123, wherein the fragment comprises heavy chain and light chain variable domain amino acid sequences of either SEQ ID NO. 9 and SEQ ID NO. 10, or SEQ ID NO. 15 and SEQ ID NO. 16, respectively.
 19. The recombinant fully human anti-CD123 antibody fragment of claim 18, wherein the antibody has a K_(D) of at least 1×10⁻⁶M.
 20. A method for treating a CD123 positive cancer in a human subject in need thereof, the method comprising the step of administering an effective amount of the recombinant fully human anti-CD123 antibody fragment of claim 18, such that the cancer is treated.
 21. The method of claim 20, wherein the recombinant fully human anti-CD123 antibody fragment comprises heavy chain and light chain variable domain sequences of SEQ ID NO. 9 and SEQ ID NO.
 10. 22. The method of claim 20, wherein the recombinant fully human anti-CD123 antibody fragment comprises heavy chain and light chain variable domain sequences of SEQ ID NO. 15 and SEQ ID NO.
 16. 23. The method of claim 20, wherein the cancer is selected from the group consisting of non-Hodgkin's lymphoma, Burkitt's lymphoma, multiple myeloma, B chronic lymphocytic leukemia, B and T acute lymphocytic leukemia, T cell lymphoma, acute myeloid leukemia, hairy cell leukemia, Hodgkin's Lymphoma, and chronic myeloid leukemia.
 24. The recombinant fully human anti-CD123 antibody fragment of claim 18, wherein the fragment is classified as an IgG.
 25. The recombinant fully human anti-CD123 antibody fragment of claim 24, wherein the fragment is an IgG1 or an IgG4.
 26. The recombinant anti-CD123 antibody fragment of claim 18, wherein the fragment is selected from the group consisting of a Fab, a Fab′, a F(ab′)2, an Fv, and a single-chain antibody.
 27. A single chain anti-CD123 antibody that binds to CD123, comprising heavy chain and light chain variable domain amino acid sequences of either SEQ ID NO. 9 and SEQ ID NO. 10, or SEQ ID NO. 15 and SEQ ID NO. 16, respectively, and wherein the heavy chain variable domain and the light chain variable domain are connected by a peptide linker.
 28. The single chain anti-CD123 antibody of claim 27, wherein the antibody has a K_(D) of at least 1×10⁻⁶M.
 29. A method for treating a CD123 positive cancer in a human subject in need thereof, the method comprising the step of administering an effective amount of the single chain anti-CD123 antigen-binding fragment of claim 27, such that the cancer is treated.
 30. The method of claim 29, wherein the anti-CD123 single chain antibody comprises heavy chain and light chain variable domain sequences of SEQ ID NO. 9 and SEQ ID NO.
 10. 31. The method of claim 29, wherein the anti-CD123 single chain antibody comprises heavy chain and light chain variable domain sequences of SEQ ID NO. 15 and SEQ ID NO.
 16. 32. The method of claim 29, wherein the cancer is selected from the group consisting of non-Hodgkin's lymphoma, Burkitt's lymphoma, multiple myeloma, B chronic lymphocytic leukemia, B and T acute lymphocytic leukemia, T cell lymphoma, acute myeloid leukemia, hairy cell leukemia, Hodgkin's Lymphoma, and chronic myeloid leukemia. 